DEPARTMENT OF THE INTERIOR.
BULLETIN
THE UNITED STATES
GEOLOGICAL AND GEOGRAPHICAL SURVEY
OF
THE TERRITORIES.
F. V. HAYDEN,
U. Ss. GHEOQLOGIST-IN-CHARGE.
HS:3/2).
MEARNS COLLECTICK
WiO@dL Wenn). WE: ay
WASHINGTON: GOVERNMENT PRINTING OFFICE. 1882.
Sito
s
By :
PREFATORY NOTE.
U. S. GEOLOGICAL AND GEOGRAPHICAL Pia, © SURVEY OF THE TERRITORIES, Washington, July 31, 1882.
Bulletin No. 3 completes Volume VI and ends the series. With this number are issued index, title-page, table of contents, list of illustra- tions, &c., for the whole volume. The separately published numbers should be preserved for binding, as there is no issue of the Bulletins in bound volumes, and as back numbers cannot always be supplied to complete deficient files.
In issuing the final volume of Bulletins, a word regarding the origin and progress of this publication will not be out of place. The issue began in 1874, when it was found desirable to establish more ready means of communication with the public and with scientific bodies than the regular reports of the Survey afforded; the design being to publish, without the delay incident to the appearance of more elaborate and ex- tended articles, such new or specially interesting matter as should be contributed to the general results of the explorations under my charge by the members or the collaborators of the Survey. The practical im- portance of prompt measures in such cases is well recognized, and sufii- ciently attested by the success which the Bulletins have achieved.
The First and Second Bulletins, which appeared in 1874, are sepa- rately paged pamphlets, without ostensible connection with each other or with subsequent ones, but together constituting a “First Series” of the publication. Bulletins which appeared in 1875, being those of a ‘Second Series” and six in number, are continuously paged. With No. 6 were issued title, contents, index, &c., for all the numbers of both “series” which had then appeared; the design being that these should together constitute Volume I, in order that the inconvenient distinction of “series” might be dropped. |
With Bulletin No. 1 of 1876, the publication was established as an annual serial; the four consecutively paged numbers of that year con- stituting Volume II.
The four Bulletins of 1877 constitute Volume ITI.
The four Bulletins of 1878 form Volume IY.
The four Bulletins of 1879 and 1880 constitute Volume V, and Volume VI, which contains three numbers, issued during 1881 and 1882, closes
the publication. It is to be regretted that Article I of No. 3 remains iii
IV PREFATORY NOTE.
incomplete, owing to the unfortunate sickness of the author, Professor Allen, which prevents the continuation of the abo srra uy of the Cetacea and Sirenia in the serial. Volumes IV and V were issued under the supervision of Dr. Elliott Coues, U.S. A., and Volume VI was.completed by W. H. Holmes. F. V. HAYDEN, United States Geologist.
CONTENTS OF THE WHOLE VOLUME.
BULLETIN No. 1.—february 11, 1881.
I.—The Vegetation of the Rocky Mountain Region, and a comparison with that of other parts of the world. By Asa Gray and Joseph D.
HOO KOM a seteniae see sis ne neeeteweiec asm snciscmeten ees hte o success II.—On some new Batrachia and Reptilia from the Permian Beds of Texas. yeh Dy Cone) sacscac essa see eieks se siseee emelesi oes eceecl cca. Jae III.—On a Wading Bird from the Amyzon Shales. By E. D. Cope -..-..----- IVY.—Osteology of Speotyto Cunicularia var. Hypogea. By R. W. Shu- feldt, Acting Assistant Surgeon, U. S. Army -...--.....---.-------- V.—Osteology of Eremophila Alpestris. By R. W. Shufeldt, Acting As- SIS CAMEO UE MOM, Wes Os ANI Ye racis mein sta is erate Eee ne nll ahe ei aminls ViI.—Preliminary list of the North American species of Agrotis, with de- ScRIpoonsi by A. Rs Globe) sooc) =. oo ae eee eee seer a ae ermciceme VII.—On the Nimravide and Canide of the Miocene Period. By E. D.
BPD OOM Sae arjsemia cia et cicis ateiattaciors sis tee eee ema eine ete reine ones
BULLETIN No. 2.—September 19, 1881.
IX.—Annotated list of the Birds of Nevada. By W. J. Hoffman, M.D ..-. X.—North American Moths, with a Preliminary Catalogue of Species of
Hadenay andy Pola. By Ac he GLOUG) aso qos = aanys oe ees ee XI.—The Tertiary Lake Basin of Florissant, ee between South and Hayden Parks. By Samuel H.\Scudder,jge2<.-- - 25-2 52--22 c2e6 5-0 XII.—Revision of the Genus Sciurus. By E-L. Trouessart .......--...----
XIII.—Osteology of the North American Tetraonide. By R. W.Shufeldt---. XIV.—Osteology of Lanius ludovicianus excubitorides. By R. W. Shufeldt.. XV.—Review of the Rodentia of the Miocene Period of North America. By
ee Di COpe eas sack ses ka ostaaise cre oe oa eee aeteeette mea spars ols Soe XVI.—On the Canide of the Loup Fork Epoch. By E. D. Cope.........-.-. XVII.—On a Cray-fish from the Lower Tertiary Beds of Western Wyoming. By A. 8. Packard - Sema SFe enema Seideiee Sersaa eh ad a ses alsaa5 Sys
BULLETIN No. 3.—August —, 1882.
XYVIII.—Preliminary List of Works and Papers relating to the Mammalian Or- ders Cete and Sirenia. By Joel Asaph Allen.............--.- XIX.—New Moths, with Partial Catalogue of Noctuz. By A.R. Grote, ia M. XX.—New Moths, principally collected by Mr. Roland Thaxter, in Maine, with notes on noxious species, and remarks on classification. By A. eG EGLO aerate cena cto tac on a Pesan, cision ein sale eee nee
Page.
119
149
165
183
203 207 279 301 309 dol
361 387
391
LIST OF ILLUSTRATIONS.
PLATES. 1A i Skeletonlof: Speotyto) Cumicmlariaes ses) 5-- = seeeeee eee eee Pi ue —Osteolosy of Speobyto Cunicularia .-e- 2-5-2 ee eee eee eee Py LiL Osteolory ot Speotyto Cunicularia see soe ee selene eee PI Vi— Osteolosyjot Lremophila Alpestris\].--—5 425 eee see eee Py Ve Osteology of American Tetraonidas 225.202 cee =e a= ae eee Pei Osteolocysot American etraonidse sees eee een eee eee eee eee evade —Osteolooysot American mletraonid =a sae— eee eee eee eee eee PIS Vill —Osteolosy of American Metraonidee -25.55 -esacs 42 ea-e ose eee eee eee ese ——Osteolocyiot American Retraonidce-sseeeeeeeeeee ese se Seco eee PI, -x¢-_Osteology of American) letraonidiae-sa-enee eee eee ee ae eee eee ie scle—— OSbeology ote American etraomidles ese ree sella — OS ceoloovsorAmenican he braonid sys ee eee ee ee eee slate PT xthl—Osteology of American Tetraonidss 22eee sss ea- 4-2 a eee eee eee
Pl. XIV.—Osteology of Lanius Ludovicianus excubitorides ........-...- -.<--
Fig. Fig. Fig. Fig. Fig. Fig.
CUTS IN TEXT.
—Anolesioriskl lon Hremophila n= acess. =e see eer Seis ete eee —Showing distribution of Vegetation _.-__.-----._.-. 2-2: 2.5 —Slowine distribution of Veretation ----5.---4s--2 eee See ee eee a Manrof Nevada Sense cor fe. joe Sack. coeeeece ee ees odicia Joe eee —-Mapiofbionssant, Colorado... -.- .. +--+ -<-eseeeeeeee eee eee = Mossi Cray fel co < octae< soe sci vin a, nlnie ntbneie ici ea aivee eee Gee ee
vi
DHPARIMENT OF THE INTHRIOR. UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY. F. V. HAYDEN, U. 8. GEOLOGIST-IN-CHARGE.
BULLETIN
THE UNITED STATES
GEOLOGICAL AND GEOGRAPHICAL SURVEY
OF
THE TERRITORIES.
VOLUME VI....-NUMBER 1.
WASHINGTON: GOVERNMENT PRINTING OFFICH. February 11, 1881.
BULLETIN
OF THE
UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY OF THE TERRITORIES,
NUMBER 1.
VoLumeE VI. 1880.
Art. 1.—The Vegetation of the Rocky Mountain Re- gion and 2a Comparison with that of other Parts of the World.
By Asa Gray and Joseph D. Hooker.
I. THE VEGETATION OF THE ROCKY MOUNTAIN REGION.
The vegetation of the wide central tract which lies between the At- lantic United States and those which border on the Pacific is replete with interest and importance, both scientific and economical. We are to sketch its general features, as made known to us by personal obser- vation, by the published observations of others, and by the botanical studies to which we have been devoted. For doing this to much pur- pose, it is necessary to compare or to contrast the vegetation of the dis- trict in question with that of the more fertile regions on both sides, and with a somewhat similar wide interior district in another part of the northern temperate zone.
By “the Atlantic States,” as contradistinguished from those of the Pacific, we here mean not only those which touch upon the Atlantic Ocean, but also those which border the Mississippi River, on its western as well as its eastern side; the great woodless plains being taken as their western limit. The term “Rocky Mountain Region,” here used in its widest sense, and in the lack of a better appellation, we propose to apply in general in such wise as to include the gradually elevated pla- teau which flanks the eastern base of the Rocky Mountains on the one hand, and the equally elevated district or plateau, thickly traversed by mountain ranges, which extends westward to the eastern base of the Sierra Nevada of California, and the Cascade Mountains further north. As to the Rocky Mountains themselves, it is most convenient and nat- ural, from our point of view, to comprise under this general designation all the ranges as far west as the Wahsatch inclusive.
We understand the term Cordilleras, brought into use by Professor
1GB
2 BULLETIN UNITED STATES GEOLOGICAL SURVRKY. | Vol VI.
Whitney, to be a comprehensive appellation for the whole system of mountains, from the most eastern Rocky Mountains to the Sierra Nevada inclusive, and the continuation of the latter in the Cascade Mountains of Oregon and British Columbia. The region which we are to treat botanically might take the name of the Cordilleran Region of North America. But it will, on several accounts, be better to adhere in this essay to the designation used in our title. For, although the term ‘“cor- dilleras” would be the only appropriate one if we had the whole vast mountain system in view, from Patagonia to the Arctic sea-coast, it 1s a term which belongs primarily and mainly to South America, and our survey is to embrace only a few parallels of latitude, in fact just those which contain the ranges which early took the name of the Rocky Mount- ains, both at the north, where they were traversed by Lewis and Clarke at the beginning of this century (1803-1806), and at the south, where they were reached on the frontiers of New Mexico by Pike a year or two later.
With these Rocky Mountains proper, 7. e. the eastern and dominating ranges, as the central line of our field of view, the horizon should extend eastward to where the gradually subsiding plain becomes green with a rich prairie vegetation, to be at length fringed with forest, and westward to the base of the Sierra Nevada and the Cascades, the eastern verge of the Pacific forest region.
In a developed treatise, the physical geography and the climatie ele- ments of the region would have to pass under review, and the multi- farious and scattered botanical data would have to be collected, dis- cussed, and tabulated. We cannot undertake an exhaustive task like this, nor could we add much to what has already been done in various well- considered and well-known government reports. The climatology and the practical considerations deducible from it form the subject of Major Powell’s “ Report on the Lands of the Arid Region of the United States,” the second edition of which was issued in 1879. In the “Gen- eral Report” which forms the introduction to the botanical volume of Clarence King’s celebrated “ Survey on the Fortieth Parallel” (and which prefaces that elaborate systematic treatise which was too mod- estly styled a “Catalogue,” and so has by some been cited as such), Mr. Sereno Watson has thoroughly and ably discussed the elements of the flora of the Great Basin, exemplifying it with lists and other details. And for a district further south, Professor Rothrock, in his volume on the Botany of Wheeler’s Surveys, has within the last year published his instructive notes on the characteristic features of the botany of Colo- rado, New Mexico, and a part of Arizona. Professor Sargent has given a useful sketch of the arboreal and frutescent vegetation of Nevada in the American Journal of Science for June, 1879; and among Professor Hayden’s very important reports, that of Henry Gannett, “ On the Ara- ble and Pasture Lands of Colorado” (1875, reprinted in 1878), is note- worthy.
No.1.1 GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 3
Our sketch must be, like our observations, a rapid and cursory recon- naissince, noting some features which arrested our attention, drawing some comparisons, and suggesting inferences which seem to us probable. The phytogeography of the temperate portion of the North American continent, in broad outlines is evidently this: An Atlantic forest region; a Pacific forest region; and, between the two, the wide interior, main]* non-forest, region—the special subject of our essay; a region not easy to name nor to describe succinctly, but of which the eastern half is a vast woodless plain, gradually and evenly rising, so that its western margin is about 5,000 feet above the sea-level; then a mountain belt, the high- est ridges and peaks of which rise from 11,000 to 14,400 feet; then, shut out from moisture by these mountains on the east and the Sierra on the west, an arid interior district of plains, at an average of 5,000 feet above the sea. This is mainly desert, and is traversed by many mount- ain ranges, generally of north and south direction, and reaching an ele- vation of 9,000 or 10,000 feet, or rarely higher. This whole interior, of miles average breadth—like other great interiors not very exceptionally favored—is marked by the scantiness or absence of arboreal vegetation and of rainfall, the former being in great measure dependent on the lat- ter. Its plains are treeless except along water-courses; the mountains bear trees along sheltered ravines and on their higher slopes, upon which there is considerable condensation of moisture; but, whenever they rise to a certain height (about 11,000 feet in latitude 37° to 419), they are woodless from cold and other hardship attending elevation, although they enjoy an abundant condensation of moisture, mostly in the form of snow.
The Rocky Mountain region may be therefore divided vertically into three botanical districts:
1. An arid and woodless district, which oceupies far the greater part of the area.
2. A wooded district, in some places covering, in others locally adorn- ing, the mountain slopes.
3. An alpine unwooded district above the belt where trees exist. But in some places, slopes woodless from dryness merge into tracts woodless from cold, no proper forest belt intervening.
These three botanital districts may be separately investigated.
The smallest in area—since it is restricted to mountain summits and the least peculiar, is—
I.—THE ALPINE REGION.
Botanically the alpine regions of the temperate zone in the northern hemisphere are southward prolongations of arctic vegetation, almost pure in the boreal parts, but more and more mixed with special types in lower latitudes, these special types being a part of the flora which is characteristic of each continent in those latitudes.
4 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VI-
Leaving out of view a considerable number of temperate species which here and there become alpestrine or persist in dwarfed forms within some truly alpine regions, the alpine flora of the United States does not
‘comprise a large number of species. It may be useful to present a tab-
ulated list of them, 7. ¢., of the phenogamous portion, under three heads, placing the ampler Rocky Mountain alpine flora in the center and the more restricted Atlantic and Pacific alpine floras one on each side.
It will be understood that the survey is limited to the United States proper, reaching latitude 47° on the Atlantic and 49° 40’ on the Pacific side, in all of which the proper alpine flora is confined to high altitudes, from about 5,000 to over 14,000 feet above the sea-level. On the At- lantic side it is only a matter of a few isolated summits in New England and Northern New York, the Alleghanian or Apalachian chain and its' dependencies not being high enough in New York and Pennsylvania, and being in too low latitude notwithstanding their greater elevation in the Carolinas, to have more than alpestrine vegetation, although a few properly alpine species linger on the summits. On the Pacific side we have to do only with the Sierra Nevada and its northern prolongation ; and there, too, we make latitude 47° the northern limit, because north of that parallel, we cannot at present well determine the limit between. what belongs to the Rocky Mountains and what to the continuation of the Cascade Mountains.
The species which are not arctic are distinguished by italic type; when the genera are peculiar to the region, the generic name is printed. in small capitals. ‘To save space in the columns, the names are printed without reference to authorship.
The left-hand column is so insignificant, that it might have been omitted. We cannot amplify it by adding alpine plants from farther north, such as the stragglers about the Gulf of Saint Lawrence and the Labrador flora, for these are found nearly at the sea-level and are ex- tensions of the proper arctic flora.
Atlantic United States Alpine. Rocky Monntain Alpine. Pacific United States Alpine.
Thalictrum alpinum.
Anemone narcissifiora. Anemone narcissiflora. Anemone occidentalis (A. Baldensis Hook). Ranunculus Hschscholtzii. Ranunculus Eschscholiziz. Ranunculus pygmeaus. Ranunculus pygmeus.
Ranunculus adoneus. Ranunculus Macauleyi. Ranunculus oxynotus.
Papaver alpinum (nudicaule). Papaver alpinum (nudicaule).
Parrya macrocarpa. Parrya macrocarpa. Cardamine bellidifolia. Cardamine bellidifolia. Cardamine bellidifolia.
Draba aurea. Draba aurea.
Draba alpina. Draba alpina.
Draba hirta or arctica.
Draba crassifolia. Draba crassifolia.
Draba stellata or muricella. Draba stellata or muricella,
;Draba ventosa. Draba eurycarpa.
Draba Douglasii. Draba 5.2
No. 1]
GRAY AND HOOKER ON THE ROCKY, MOUNTAIN FLORA.
5
Atlantic United States Alpine.
Silene acaulis.
Arenaria Grenlandica. Arenaria yerna or vars.
Astragalus alpinus.
Rubus Chamzmorus. Dryas octopetala ?
Geum radiatum, Peckiv. Potentilla frigida.
Sibbaldia procumbens.
Saxifraga rivularis.
Saxifraga stellaris.
‘Saxifraga oppositifolia. Sedum Rhodiola.
Solidago humilis, var. alpina.
(Greenland.)
-Gnaphalium supinum.
Rocky Mountain Alpine.
Smelowskia calycina. Thlaspi alpestre. Lychnis (Melandrium) Kingii.
Silene acaulis. Cerastium alpinum.
Avenaria verna or vars. Avenaria Rossii.
Arenaria biflora.
Arenaria arctica.
Sagina nivalis.
Claytonia arctica, megarrhiza. Calandrinia pyymeen. Lrifolium nanwn.
Trifolium andinum. Trifolium dasyphyllum. Trifolium Parryi. Astragalus calycosus. Astragalus alpinus. Oxytropis podocarpa. Oxytropis Uralensis, arctica. Oxytropis nana.
Oxytropis multiceps.
Rubus Chamzmorus. Rubus arcticus.
Dryas octopetala and var. Geum Rossii.
Potentilla frigida?
Potentilla diversifolia. Potentilla nivea.
IvESIA Gordont.
Sibbaldia procumbens. Saxifraga adscendens. Saxifraga Jamesii. Saxifraga rivularis. Saxifraga debilis. Saxifraga cernua. Saxifraga Hireulus. Saxifraga chrysantha.
Saxifraga stellaris.
Saxifraga punctata. Saxifraga Dahurica. Saxifraga nivalis. Saxifraga czespitosa. Saxifraga bronchialis. Saxifraga tricuspidata. Saxifraga flagellaris. Saxifraga oppositifolia. Chrysosplenium alternifolium. Sedum Rhodiola. Sedum rhodanthum. Epilobium latifolium.
CYMOPTELUS alpinus. CYMOPTERUS nivalis.
APLOPAPPUS pygmeus. APLOPAPPUS Lyallit. Solidago humilis, var. alpina.
| TOWNSENDIA condensata.
TOWNSENDIA Rothrockii. Aster andinus. Aster alpinus.
Erigeron uniflorum. Brigeron grandifiorum. Drigeron ursinum. Brigeron radicatum. Antennaria alpina.
ACTINELLA grandiflora. ACTINELLA Brandegei. Hurska algida. HAUrsrA nana.
Pacific United States “Alpine,
ttl ore
Smelowskia calycina. Thlaspi alpestre.
Lychnis (Mel.) Oalifornica. Silene acaulis. Cerastium alpinum.
Arenaria verna or vars.
Arenaria biflora. Avenaria arctica.
Calandrinia pygmed.
Astragalus alpinus.
Briogynia pectinata,
Rubus arcticus. Dryas octopetala.
Potentilla gelida. Potentilla Breweri. Potentilla diversifolia.
Potentilla villosa. IVESIA Gordoni. Ivresia Muirii. Sibbaldia procumbéns.
Saxifraga rivularis.
Saxifraga cernua.
Saxifraga Tolmier. Saxifraga stellaris.. Saxifraga bryophora. Saxifraga punctata. Saxifraga Dahurica. Saxifraga nivalis. Saxifraga czespitosa. Saxifraga bronchialis. Saxifraga flagellaris. Saxifraga oppositifolia. Chrysosplenium alternifolium. Sedum Rhodiola.
Epilobium latifolium. Epilobium obcordatum.
CYMOPTERUS cinerascens. CYMOPTERUS Nevadensis.
Aplopaoppus Lyallit.
Brigeron compositum. Erigeron uniflorum.
Brigeron ursinum.
Antennaria alpina.
aa
6
BULLETIN UNITED
Atlantic United States Alpine.
Artemisia borealis, L. Sup.
NABALUS nanus. NaBALUS Booitit.
Vaccinium cespitosum.
Arctostaphylos alpina. Cassiope hypnoides.
Bryanthus taxifolius. Rbododendron Lapponicum.
Loiseleuria procumbens. Diapensia Lapponica.
Veronica alpina. Castilleia pallida, var sept.
Euphrasia officinalis (gracilis).
Oxyria digyna.
Polygonum viviparum.
Salix herbacea. Salix Uva-Ursi? Empetrum nigrum. Habenaria obtusata.
wuzula spicata. zuzula arcuata.
STATES GEOLOGICAL SURVEY. Rocky Mountain Alpine. | Pacific United States Alpine.
Artemisia borealis. Artemisia scopulorum. Artemisia arctica. Senecio Fremontt. Senecio anuplectens. Senecio Soldanella. Crepis nana. Hieracium triste.
Taraxacum levigatum. Campanula uniflora.
Vaccinium cespitosum. Arctostaphylos alpina.
Cassiope tetragona. Cassiope Mertensiana.
Bryanthus empetriformis.
Bryanithus glanduliflorus. Rhododendron Lapponicum.
Primula angustifolia. Primula Parryit.
Douglasia nivalis. Douglasia montana. Androsace Chamejasme. Gentiana barbellata. Gentiana tenella. Gentiana propingua. Gentiana arctophila. Gentiana prostrata. Gentiana glauca. Gentiana frigida.
Gentiana Parryt.
Phlox bryoides.
Phlox muscoides.
Phlox ccespitosa.
Giuia Brandeget. Polemonium confertum. Polemonium viscosum. .Polemonium humile. Hritrichium nanum. Mertensia alpina. ‘CHIONOPHILA Jamesit.
SYNTHYRIS alpina.
Veronica alpina.
Castilleia pallida, var. sept.
Castelleta breviflora. ~Huphrasia officinalis (gracilis). | Pedicularis Grenlandica. Pedicularis Parryi.
Pedicularis scopulorum. Pedicularis flammea. Paronychia pulvinata. Hriogonum undrosaceum.
Briogonwm Kingit. Koenigia Islandica. Oxyria digyna.
Polygonum viviparum. Polygonum minimum. Salix arctica, var. Salix reticulata.
Salia phlelophylla.
Habenaria obtusata. .Tofieldia palustris. ‘Tofieldia coccinea. Lloydia sentina. Luzula spicata. Luzula arcuata.
Artemisia arctica. Senecio Fremonti.
Crepis nana. Hieracium triste.
Vaccinium cespitosum.
Cassiope tetragona. Cassiope Mertensiana. Cassiope lycopodiotdes. Bryanthus Brewer. Bryanthus empetriformis.
| Bryanthus glandulijfiorus.
Primula angustifolia.
Primula suffrutescens.
Androsace Chamejasme,
Gentiana Newberryt.
| Phlox ceespitosa.
Polemonium confertum.
Polemonium humile. Eritrichium nanum.
Veronica alpina. Castilleia pallida, var.
| Pedicularis Grenlandica.
| Pedicularis ornithorrhyncha.
| Briogonum incanum. | Briogonum Lobbit.
Briogonum pyrolefolium.
Oxyvia digyna. Polygonum Shastense. — Polygonum viviparum.
Salix arctica, var. Salix reticulata. Salix phlelophylla.
Lloydia sentina. Luzula spicata. Luzula areuata.
[ Vol. VI.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA, 7
Atlantic United States Alpine. Rocky Mountain Alpine. Pacific United States Alpine.
Juncus trifidus. Juncus triglumis. Juncus biglumis.
Juncus Parryt. 4 Juncus Parryt. Juncus Drummond. Juncus Drummondii. Juncus castaneus. Juncus castaneus.
det Actua Juneus chlorocephalus. Kobresia scirpina. Kobresia caricina.
Carex Pyrenaica. Carex Pyrenaica. Ret Carex nigricans. Carex nigricans. Carex scirpoidea. Carex scirpoidea. Carex scirpoidea.
Carex obtusata. Carex Lyoni. Carex capitata. Carex ecapitata. Carex Breweri. Carex incurva. Carex atrata. Carex atrata. Carex atrata. Carex alpina. Carex alpina. Carex fuliginosa. Carex frigida.
Carex feetida. Carex fotida,
Carex lagopina. Carex lagopina. Carex rigida. Carex rigida. Carex rariflora. Carex rariflora.
Carex podocarpa. Carex podocarpa. Carex capillaris. Carex capillaris.
Carex filifolia. Carex filifolia.
Carex concinna. Carex luzulefolia. Alopecurus alpinus. Phleum alpinum. Phleum alpinum. Phleum alpinum. | Agrostis rubra, etc. Calamagrostis Pickeringit. |
Hierochloa alpina. Hierochloa alpina. Trisetum subspicatum. Trisetum subspicatum. Trisetum subspicatum. Aiva atropurpurea. Poa laxa. | Poa laxa. Poa arctica. Poa alpina. Poa alpina. Poa alpina. . | Festuca brevifolia or rubra. Festuca brevifolia or rubra. 52 sp. 184 sp. 111 sp.
The analysis of this alpine flora need not detain us. The botanist sees at a glance that it is the arctic flora, or rather prolongations of it, ex- tended southward aiong the mountains of sufficient elevation, with cer- tain admixtures of types pertaining to the vegetation of the regions.
The peculiar elements in the scanty alpine flora of the Eastern United States are only five species, viz: One grass of arctic affinity, Calamagrostis Pickeringti ; an orchid, Habenaria obtusata ; a Geum, which has its princi- pal home on the subalpine summits of the Alleghanies farther south, and is nearly represented by a species on the Northern Pacific coast; and two species of Nabalus, which will be allowed to be altered states of species peculiar to North America and nearly peculiar to the Atlantic side.
The Pacific alpine flora has a higher proportional number of non-arctic species, as must needs be, considering its long stretch through so many parallels of latitude; but the number pertaining to non-arctic genera is small. They are—
Calandrinia pygmea. Cymopterus, 2 species. EBriogynia pectinata. Aplopappus Lyallii. Ivesia, 2 species. Eriogonum, 3 species.
All of them are of genera peculiar to America. Besides these, only 38 species are peculiar to America, and between a third and a quarter
8 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
of these are known to extend to Arctic America. Of the whole 111 species about 50 are not known in Europe and Asia in identical species. The list of Rocky Mountain alpine species reaches the number of 184. Those of the Sierra in California, and northward up to the British boundary, to 111. Those of the mountains in the northeastern part of the Atlantic States
_. (the Alleghanies, though reaching a greater altitude, are not high enough
for the latitude to have any alpine vegetation, though they verge on it) are only 52.
The comparative meagerness of this last list is not surprising when we consider how very restricted the alpine area altogether is in Maine, New Hampshire (which has most of it), and the northeastern corner of New York. And we have not taken into account the arctic-alpine spe- cies which descend to the sea-level on the shores of the Gulf of Saint Lawrence, nor the few which occur on the bleak northern shore of Lake Superior. The latter, as some one has well suggested, owe their exist- ence or continuance there neither to the absolute elevation nor to the latitude, but to the moist bleakness of a wind-swept coast, which gives them congenial summer conditions, on ground which forest cannot stand upon, Owing to the severe exposure. Yet this forest resumes its sway northward, as soon as some shelter is given.
The Pacific alpine region, notwithstanding its long stretch along the mountain tops of a continuous but narrow north and south range, is also a restricted one. In California only the very culminations of the Sierra Nevada can be said to be alpine, and they are too arid in summer for the development of a true alpine flora. In Oregon and Washing- ton Territory there is equal height under more northern parallels of latitude, abiding snow, and summer rain. The botany of these heights is far from well known. Probably all the arctic species of the Rocky Mountain column also belong there, and a fair share of exclusive species.
It is difficult to say what are or are not alpine species in the Sierra. Nevada, especially southward, where, notwithstanding the heavy winter fall of snow, the higher elevations are unwooded from dryness as much as from cold. But, as we have excluded species which show themselves to be at home at lower altitudes, and have included all arctic-alpine types, the number of questionable character is very small.
Nor, except that we know their ranges and aptitudes better, is there much less difficulty in drawing a line between truly alpine and alpes- trine species in the other regions. There are a goodly number of spe- cies which are normal to low altitudes or to the sea-level in the northern temperate zone, such as Campanula rotundifolia, Taraxacum Dens-leonis, Androsace septentrionalis, Eriophorum alpinum, polystachyon, &e., and Festuca ovina, which also flourish in an alpine station. And, indeed, these same species, and others like them (such as Hrigeron compositum, which flourishes at the base as well as on the highest summits of the Rocky Mountains, and also in Greenland), make a part of the extreme
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 2
arctic flora. Any list will therefore be to some extent arbitrary. For example, in the Atlantic alpine list, while Cardamine bellidifolia, Silene acaulis, Sibbaldia procumbens, Gnaphalium supinum, Rhododendron Lappo- nicum, Diapensia Lapponica, and the like, are strictly and exclusively alpine, Arenaria Grenlandica and Geum radiatum (Peckii) are included for reasons which any botanist who has ascended these mountains will appreciate, although a form of the Arenaria sparingly oceurs at low levels in Southern New England and New York, and both on the tops of the higher Alleghanies, where no characteristically alpine species accompany them, and where such summits as are bare of trees are not woodless on account of cold or any other incident of mere elevation.
Notwithstanding the geographical extent of the country over which it is spread, the North American alpine flora is meagre in species com- pared with that of Europe. This will abundantly appear in the com- parison to be made in another part of this report. Reasons connected with geographical configuration and climate will account for this, but it must also be remembered that the botany of the European Alps is thoroughly known; that of the Broeey and other western mountains quite imperfectly 5h
Ii.—TuHE ForREST REGION. 1. Its trees.
The most conspicuous portion of the vegetation of a country, and the most important under more than one point of view, is its trees. Their importance is most manifest in the district under consideration, where less than a quarter of the area is capable of producing them, and of which, owing to fires and other causes, only about half of what Major Powell designates as “ timber regions” are actually covered with forest. Toward the north the case is more or less altered, especially in British America, where, in a wide tract with moderately abundant and well distributed rainfall, and summers not excessively warm, the Atlantic and Pacific forests join and intermingle. Southward, and indeed nearly up to the northern boundary of the United States, trees are borne only on the mountains and high plateaux, and along the immediate banks of streams descending from these.
The species of the whole Rocky Mountain region (taken in the widest extent) which may claim the name of trees—even of tree-like shrubs— are not long to enumerate.* They are these:
Sapindus marginatus, Willd. Morus microphylla, Buckley. Acer grandidentatum, Nutt. Populus angustifolia, James. Negundo aceroides, Moench. ale balsam ile L.
*We are much ataedsi in ree Seboeenn by Prof. C. ‘Ss. Sargent’s Edaeioua on 1 The Forests of Central Nevada, in Amer. Journ. Sci., ser. 3, xvii, June, 1879, and by his Catalogue of the Forest Trees of North America, 1880, printed by the United States Census Bureau.
10
Olneya Tesota, Gray. Parkinsonia Torreyana, Watson. Prosopis juliflora, DC.
Prosopis pubescens, Benth. Acacia Greggit, Gray.
Prunus Pennsylvanica, lL. * Cercocarpus ledifolius, Nutt. Pyrus sambucifolia, Cham. & Schl. Orateegus—near rivularis, Nutt. Amelanchier alnifolia, Nutt. Cereus giganteus, Engelm. Sambucus glauca, Nutt. Arbutus Menziesvi, Pursh, var. Fraxinus anomala, Torr. Fraxinus pistacicfolia, Torr. Fraxinus viridis, Michx., f. Chilopsis saligna, Don. Platanus Wrightii, Watson. Juglans Californica, Watson. Juglans rupestris, Engelm. Quercus Emoryt, Torr.
Quercus hypoleuca, Kngelm. Quercus undulata, Torr.
Betula occidentalis, Hook.
BULLETIN UNITED STATES GEOLOGICAL SURVEY.
[ Vol. Vi,
Populus Fremontii, Watson.
Populus monilifera, Ait.
Populus tremuloides, Michx.
Populus trichocarpa, Torr. & Gray.
Juniperus occidentalis, Hook.
Juniperus Californica, Carr.
Juniperus Virginiana, L.
Juniperus pachyphlea, Torr.
Abies concolor, Lindl.
Abies subalpina, Engelm.
Pseudotsuga Douglasti, Carr.
Picea Engelmanni, Engeln.
Picea pungens, Engelm.
Larix oecidentalis, Nutt.
Pinus edulis, Engeln.
Pinus flexilis, James.
Pinus aristata, Engelm.
Pinus Chihuahuana, Engelm.
Pinus contorta, var. Murrayana, Eng.
Pinus monophylla, Torr.
Pinus ponderosa, Dougl., var. scopu- lorum, Engelm.
Pinus Arizonica, Kugelm.
Yucea brevifolia, Kngelm.
This mere botanical enumeration of about fifty species of trees, or at least arborescent plants, gives no proper idea ot the arboreal flora as it presents itself to the view of a botanical traveler. It includes all the trees we know to inhabit any part of a vast tract, extending from the eastern base of the Rocky Mountains to the eastern base of the Sierra Nevada and Cascade ranges, and from the Mexican boundary, in lati- tude 32°, to the northern limit of forest, in about latitude 56°. The characters of the flora at the two extremes are most widely different, There is a far greater development of forest in the northern part, but it consists of the fewest species; and to the southern portion an undue appearance of richness is given toa very scanty sylva—first, by the enu- meration of so many species which are only arbuscule in their best estate, and are commonly mere shrubs; second, by including species which belong only or mainly to the Mexican frontier region—to the south- ern part of Arizona and New Mexico.
Of the latter sort are Yucca brevifolia, the only monocotyledonous arbo- rescent species (tree it cannot well be called); the giant Cactus, Cereus giganteus, of the Lower Giladistrict; Pinus Chihuahuana and P. Arizonica, which barely cross the Mexican line; Sapindus marginatus, Arbutus Menziesti, or what seems to be a mere geographical variety of the Californian Madroia, which is not uncommon in Mexico, and which reaches Southwestern Texas; Fraxinus anomala and F. pistaciefotia,
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA, lf
Platanus Wrightii, &c., Quercus Emoryi and Q. hypoleuca, &c. Along. with these, as equally foreign to the timber region of the Rocky Mount- ains and the accessory ranges, we should eliminate and place by them- selves those trees which are characteristic of the southern arid plains, rather than of the mountains. A few of these come into Utah and Nevada, but they mostly belong to Arizona, and to a district, which, with all its aridity, receives a portion of the subtropical summer rainfall. To this category belong—
Olneya Tesota, a peculiar genus of papilionaceous Leguminosae.
Parkinsonia Torreyana, the Palo Verde (Cercidium of authors).
Prosopis juliflora, the true Mesquite, and P. pubescens, the Screw Bean or Screw-pod Mesquite, the pods and seeds of which furnish food and forage, the bark a kind of gum-arabic, and the wood good fuel.
Acacia Greggii, the only one which in this district becomes abores- cent.
Chilopsis saligna, the Desert Willow, fringing water-courses in the arid district.
Morus microphylla, a Texas Mulberry which extends along the south- ern part of New Mexico and Arizona.
It might be expected that a fair number of trees represented in the moister and cooler district of the Northern Rocky Mountains would dis- appear from the scantier, interrupted or scattered or restricted woods of the southern mountains; but we miss from them only one of the north- ern trees above enumerated, namely, the Larch of the region, Larix occidentalis, while we miss from the northern mountains no small number of those in the southern.
This is not the place to institute a comparison between the Rocky Mountain forest and the eastern; but it may be remarked that, while angiospermous, round-headed, and deciduous-leaved trees prevail in the latter, largely in the number of species and genera and conspicuously in the extent of surface occupied, the Rocky Mountain sylva, in its char- acteristic features, is gymnospermous, spiry, and evergreen. In the importance cf its useful products, such as lumber, the difference between the two sorts, as a whole, in the Atlantic forest cannot be great. But with perhaps only one exception, that of the so-called Mountain Ma- hogany, Cercocarpus ledifolius (a small tree or more commonly a shrub), the economical value of the Rocky Mountain forest is almost wholly in its coniferous trees, and in the mountains these alone strike the eye.
Disregarding unesseutial and inconspicuous features, and eliminating those outlying small trees of the Mexican border, we may say that the Rocky Mountain forest is composed of the following species, which are arranged somewhat in the order of their conspicuousness and impor- tance :
_ Pinus ponderosa, called Yellow Pine, and sometimes Long-leaved Pine, which distinguishes it well from the next. It is acomposite species, and the form of it which we are concerned with, and to which Engelmann
12 BULLETIN UNITED STATES GEOLOGICAL SURVEY. _ [Tol-VI.
assigns the name of scopulorum (7. e., the Rocky Mountain variety), is the one to which the term “long-leaved” least applies. It is one of the largest trees of the proper Rocky Mountains, along which it ranges from latitude 51°, according to Dr. G. M. Dawson, to New Mexico, is rare on any of the ranges which traverse the Nevada desert, and takes its fullest development and predominance in California and Oregon, extending also into the central dry region of British Columbia. It becomes a large tree even on the interior mountains, in the southern part mostly on slopes between 7,000 and 9,000 feet above the level of the sea, in the most northern ceasing at three to four thousand. Its heavy and coarse- grained lumber is suitable for the ruder building and the mining pur- poses to which it is devoted.
Pinus contorta, singularly called Tamarack in California, but in British Columbia Bull or Black Pine, and in Utah Red Pine, is also a rather ° composite species, one of equally great geographical range, but in higher altitudes and latitude than the preceding. It replaces it on the mount- ains of Colorado at between eight or nine and ten or eleven thousand feet; is naturally absent from the Nevada and most of the Utah ranges; in British Columbia, according to young Dr. Dawson, ‘it is the charac- teristic tree over the northern part of the interior plateau, and densely covers great areas. In the southern part of the province it is found only on those parts of the plateau which rise above about 3,500 feet, where the rainfall becomes too great for the healthy growth of P. ponderosa. It grows also abundantly on sandy beaches and river flats at less ele- vations.” Loving moisture and coolness, it is also a coast species even as far south as Mendocino County, California, whence it extends to the Yukon River, in latitude 63°. Northeastward it gets beyond the Rocky Mountains, in latitude 56°, and is replaced by the Banksian Pine “ at the watershed between the Athabasca and Saskatchewan.” The wood is white and light (so that the tree is sometimes called Spruce or White Pine), but fairly durable; but the tree never attains a great girth. In Loudon’s Encyclopedia of Trees and Shrubs, where this species is first published on Douglas’s specimens, it is named in English “ The Twisted- branched Pine.” Douglasis thought to have given the name in refer- ence to the dead and denudated slender lower branches, which persist for a long while and curve downward and inward, but do not twist; at least this is the habit of the tree in the mountains. The trunk is per- fectly straight.
Pinus aristata of Engelmann, the only form in our region of the earlier- named P. Balfouriana of California (from which it differs only in the armed tip of the cone-scales), is well called Fox-tail Pine from the ap- pearance of the leafy branches, on which the closely set leaves persist for a dozen years. It belongs only to high mountains and to latitudes north of the forty-first parallel, and is nowhere found out of the drier districts and their immediate borders. It is a small tree, of only botan- ical interest except in the mountains of Nevada, in the southern part of
No.1] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 13
which it abounds at the elevation of 7,500 or 8,000 feet, or rather once abounded, for, as Professor Sargent states, the trees within reach are fast being cut away to supply the mines with timbering. For this pur- pose its strong and close-grained, tough, and reddish wood is preferred to that of any other available tree.
Pinus monophylla, the single-leaved Nut Pine, is a most characteristic _ tree of the interior basin, mainly of the western and southern part of it, which it only slightly overpasses in Arizona and Southeastern Califor- nia. It is a tree of slow growth, and of only ten to twenty feetin height, yet with trunk sometimes two feet in diameter, and with white and soft resinous wood, furnishing valuable fuel, and in this region of narrow choice it is much used for making charcoal. The great importance of the tree was, and still is, in the crop of large and delicately flavored seeds which it yields, constituting a staple article of food for the Indians of the Great Basin.
Pinus edulis, the Pifion or Nut Pine of the Southeastern Rocky Mountains, extends from the Arkansas to New Mexico and Arizona, a tree not larger than the foregoing, also has its importance in its edible seeds, and in the value of its wood for fuel.
Pinus flexilis, the White Pine of the Rocky Mountains, and belonging to the same general section as the Atlantic White Pine, but peculiar in its thick cones and good-sized edible seed, inhabits the higher region of the Rocky Mountains from Montana to New Mexico and the higher Nevada ranges. What is considered as a short-coned variety of it (albi- caulis) is the highest tree, commonly reduced to a shrub, on and around alpine summits of the Sierra Nevada throughout allits length, and even northward in the Cascade Ranges to latitude 53°, in British Columbia. In the Rocky Mountain region this tree becomes large enough to be sawn into boards; and its ight and soft wood is the best substitute for the Eastern white-pine lumber.
Pseudotsuga Douglasii, the Douglas Spruce, the most valuable timber tree of the west coast (with the possible éxception of the Redwood), is hardly one of the second rank in such of the interior districts as it in- habits. But it is apparantly absent from all the ranges west of the Uintas and south of the forty-second parallel until the western slope of the Sierra Nevada is reached, and is not very abundant in those of Col- orado and New Mexico. It extends along the northern Rocky Mount- ains almost to latitude 54°, and a stunted variety descends on its east- ern flanks. It is found scattered among other Conifer at middle ele- vations. But from Oregon to British Columbia, toward the coast and jn the river valleys, this noble tree forms entire and vast forests, and takes a development in size and in numbers which is truly extraordi- nary. A large-fruited variety (macrocarpa) occurs at the southern ex- tremity of the Sierra Nevada at no great elevation, and extends even into Mexico.
Picea Engelmanni (Abies Engelmanni of Parry, the discoverer), the
14 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
Spruce of the higher Rocky Mountains, is an important and good-sized timber-tree. It forms the principal part of the forest in Colorado between 8,500 and 11,000 feet, and at the upper tree-line is dwarfed to a Shrub, accompanying Pinus contorta, but growing also at higher ele- vations. It is the representative of the Atlantic Spruces, in aspect and in the character of the lumber resembling Black Spruce, while the cones are just intermediate between those of the White Spruce and of the fol- lowing. Distinct as they are on the whole in character and in station, it does seem as if these ran together in a series of specimens; while, on the other hand, on its northeastern limits, between the Peace River plateau and the Athabasca, east of the Rocky Mountains, in latitude 549 and 55°, P. Engelmanni seems to pass into P. alba. This species extends southward into Arizona, westward somewhat into the higher mount- ains of Nevada, and northwestward into the interior plateau of British Columbia. It should there be studied in its relations to P. Sitchensis of the northwest coast, the original Abies Menziesii.
Picea pungens, as Dr. Engelmann now calls it, the “Abies Menzies” of Colorado, to the Rocky Mountains of which it is nearly confined, belongs to an elevational range just beneath that of P. Hngelmanni, being sparsely associated with Pinus ponderosa, while the latter attends (and generally dominates) P. conterta, both, however, affecting moister soil, as is the habit of the Spruces. The timber of the two is probably not unlike. The rigid and prickly-pointed leaves render the name of P. pungens appropriate. This species takes kindly to cultivation both in England and in the Northern Atlantic States. A portion of the young trees display a very glaucous foliage, and are much admired.
Abies concolor, the more southern of the two Firs of the Rocky Mount- ains, accompanies Picea Hngelmanni and Pinus contorta in the southern part of Colorado, and extends to New Mexico, where Fendler collected the specimens originally named. It passes westward in the mountains of Southern Utah and Arizona, and thence extends, according to Engel- mann’s identification, into and through the whole length of the Sierra Nevada, from 8,000 down to 3,000 or 4,000 feet of elevation, there becoming a pretty large tree. Its soft wood, like that of the eastern Balsam Firs, is of little account. The same is to be said of—
Abies subalpina, the more southern Rocky Mountain Fir, with smaller cones, Which most resembles the eastern A. balsamea. This, from Cen- tral Colorado and from towards the upper forest limit, extends north- ward to British Columbia, and northeastward to beyond the mountains (where it may meet and even pass into the Balsam Fir), and northwest- ward perhaps almost to the Pacific coast. Inthe United States at least, it nowhere constitutes any important portion of the forest.
Larix occidentalis, the Western Larch, belongs only to the northern part of the Rocky Mountain forest region, and to the moister portion of this. Even there it seems to be an unimportant tree.
Juniperus Virginiana, the Red Cedar and Savin, is a tree of great
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA, 15
range, as 1{ extends from the Gulf of Saint Lawrence to that of Mexico, and northwestward into British Columbia, while soufawestward it reaches Utah. In the Northern Rocky Mountains it is associated with «J. savina; in the Southern with the following species. Invaluable as its wood is, the tree is not large or abundant enough in the region under consideration to be of much account.
Juniperus occidentalis and J. Californica, the Western Red Cedars, have also a great range, a dubious variety of the former (too near a Mexican species) being the Cedar of Western Texas. The two in their various forms are very striking and characteristic trees of the dry inte- rior region. Like the eastern species, they are sometimes mere shrubs, sometimes large but low trees.
Juniperus pachyphlea, named for its very thick bark, which is likened to that of a Pine or of White Oak, takes the place of these species in Western New Mexico and adjacent parts of Arizona.
These are the trees of which the forest is composed, and which are the sole reliance for construction and fuel. Of their value to the country, of the importance to the country of their preservation, of the
sad inroads that are made upon them by fires, and of their rapid con- sumption by the inhabitants, especially in mining, it is superfluous here to discourse.
The few angiospermous trees are of quite inferior importance, and the following are the only considerable ones:
Cercocarpus ledifolius, called Mountain Mahogany, is peculiar to the mountains of the Great Basin and of its borders. Itis commonly a mere shrub, but at between 6,000 and 8,000 feet on the mountain sides it forms a small tree of 20 to 40 feet in height and a trunk which has in some eases reached the girth of 7 feet at base. The wood ‘is of a bright mahogany color, and susceptible of a beautiful polish, is exceedingly hard, heavy, and close grained, but very brittle, and so liable to heart- shake and difficult to work as to be useless in the arts. It is, however, sometimes employed for the bearings of machinery, where it is found to wear as well as metal.” “It is,” continues Professor Sargent, from whom these extracts are taken, “probably the only North American wood which is heavier than water,” its specific gravity being deter- mined by him to be 1.117 and its rate of growth so slow that “ an exam- ination of several specimens from one to two hundred years old shows an annual increase of wood only one-sixtieth of an inch in thickness.”
Negundo aceroides, the Ash-leaved Maple, is found in valleys along water-courses in the southern part of the Rocky Mountains, and as far west as the Wahsatch, and‘south to New Mexico and Arizona, while in California it is represented by a closely allied species. Its eastern ex- tension is to Canada and the borders of New England. Sugar is some- times made from its sap.
More important and conspicuous are the Poplars, which, growing wherever there is running water traversing even very arid districts,
16 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VI.
form a feature where streams issue from the mountains, and are the principal available shade-trees in places artificially irrigated, while their soft white wood is of some account in the absence of better. The Pop- lars of this kind, or the Cottonwoods of the region, are: .
Populus monilifera, the Eastern Cottonwood, which reaches the eastern slope of the Rocky Mountains, but probably does not cross them.
Populus Fremonti, a Californian species, a doubtful variety of which (or perhaps P. Mexicana) is the prevalent Cottonwood of the southern. part of the interior district.
Populus trichocarpa, a kind of Balsam Poplar, which ranges from: British Columbia to Southern California, and reaches Western Nevada..
Populus balsamifera and its broad-leaved variety, candicans, North- eastern Poplars, which reach and more or less cross the Rocky Mount- ains; and the related—
Populus angustifolia, the common Balsam Poplar of the middle part of the whole region under consideration.
Populus tremuloides, the American Aspen, is perhaps the most widely distributed of North American trees, and economically one of the most insignificant, except that the soft wood is used of late for paper pulp, and in Utah it is said to be employed in turnery and for floormg. It ranges from the Arctic coast to all the cooler parts of the Atlantic States, through the Rocky Mountains to New Mexico and Arizona, and on the western side of the continent to the middle of California. It is always a small tree, fond of moist bottoms and slopes, but on the higher mount- ains southward it takes to the higher ridges, and forms thick copses toward the upper limit of tree growth.
Betula occidentalis is a sparing but somewhat noteworthy element of the Rocky Mountain forest along its northern border in British Columbia, and is found down to Colorado and New Mexico, yet only as a shrub; also along the Sierra Nevada, where, at its southern known limit, above Owen’s Valley, and in a dry region bordering the Great Basin, “‘it is reported to be abundant, and often the main reliance of the settlers for timber for fencing and*other purposes.” (Bot. Calif., ii, 79.)
From the whole region Oaks are conspicuously absent as trees, though Quercus undulata and the forms referred to it are prominent as shrubs southward on the eastern slopes of the Colorado Rocky Mountains, and around them into New Mexico and Arizona, and although one or two Mexican types, such as Q. hypoleuca, @. Emoryi, and Q. reticulata, form small trees in the southern portions of Arizona.
The shrubby vegetation might be taken into account in connection with the forest growth. But in this regidén, where almost everything that is perennial becomes more or less lignescent, and where a predom- inant part of the vegetation of the woodless districts is suffruticose, the herbs and shrubs may as well go together.
Without entering here into a comparison of the Rocky Mountain forest with any other, it may be noted that the species are peculiar to the
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 17
region or the vicinity of it, with a few exceptions. Prunus Pennsylva- nica, Populus balsamifera, monilifera, and tremuloides, may be said to come in from the northeast, and only the last extends far into the dis- trict. ‘She Negundo and Juniperus Virginiana, with Fraxinus viridis, belong to the Atlantic forest region, and do not penetrate far, unless we count the Californian Negundo as a derivative form. The connection with Pacitic forest species is closer; and for the rest they are mainly Mexi- can plateau types, of which the botanical district in question may be regarded as a northern extension.
2. Characteristics of the herbaceous and shrubby vegetation of the Rovky ; Mountain forest region.
It was convenient and, indeed, needful to take the sylva of this region into one view, extending from British Columbia to New Mexico and Ari- zona, and from the Rocky Mountains to the western verge of the Great Basin. But in its northern part the distinction between woodland and woodless country is less marked, and the general botany is comparatively homogeneous throughout the whole latitude, the Atlantic and Pacific for- ests being there in fact confluent. Along the southern border, under very different conditions and with little and sparse forest, there is an analogous intermingling of the botanical elements, and the general vegetation of these wide-apart extremes is very different. Our personal observations were made on a middle and typical belt, on which the bot-
‘any of the central region under notice is most largely developed and purely exhibited, and where Atlantic and Pacific botany are most widely separated geographically. We shall do well, therefore, to restrict our sketches to this central belt, comprising Colorado and the southern part of Wyoming on thé east, Utah in the center, and Nevada at the west.
And when treating of the vegetation which is fostered by the forest, there is, in fact, only the eastern half of the district to consider, 7. e., the proper Rocky Mountains, the Wahsatch, and the Uintas, which connect these two systems. Far westward, throughout the Great Basin proper, there is not forest enough to impress any botanical character upon the humbler growth, although wherever there is moisture there is a vegeta- tion to correspond.
As has already been suggested, the timber region is more extensive than the grounds actually bearing forest. The contraction of the latter to its present limits is, no doubt, largely a consequence of forest fires through a long course of years; but we suppose that it is also due to an antecedent or accompanying stage of increasing desiccation of the country—a stage which, however, had passed its crisis before our ac- quaintance with the region began, the turn being testified to by the in- crease in the height of the water in the Great Salt Lake during the last thirty or forty years. We shall not strain the facts, in any case, it we inelude in the botany of the forest region, not only the plants which are now sheltered by forest, but those which extend either downward or
1G EB
18 BULLETIN UNITED STATES GEOLOGICAL SURVEY. | Vol. VI.
upward over ground which might well nourish the same kind of tree growth. This is the vegetation of the mountains, as distinguished from that of the high plains.
The peculiar shrubs of the Rocky Mountains (including the Wahsateh Range and corresponding ranges farther north) are only Jamesia Ameri- cana, a Hydrangeous genus of no near. affinity to any other, except Fendlera, which (equally unique) belongs to a lower region in New Mexico and Western Texas, Robinia Neo-Mexicana, which is an out- lying species on the southeastern border, Quercus undulata, Rubus deliciosus, Philadelphus microphyllus, Ceanothus Fendleri, and Berberis Fendleri, the latter a species of the Vulgaris type... They are all south- ern; the Northern Rocky Mountains have no characteristic shrub, as they have no characteristic tree. The principal shrubs which they share with the Pacific forest region are Acer glabrum, Prunus demissa, Rubus Nutkanus, Spirea discolor, Ribes, 3 or 4 species, Symphoricarpus oreophilus and rotundijolius, Ledum glandulosum, Salix Geyeriana, and, if we come down to such low frutescent growth, Pachystima Myrsinites, and Berberis repens.
Arctostaphylos pungens, a species of the Mexican plateau, which appears to have taken a wonderful development and diversification in California, of which it is the prevalent shrub, has reached the western portion of the Rocky Mountain Region as high in latitude as the forty-first parallel, and at an altitude which brings it among the forest shrubbery.
The shrubs which are common to this and to the Atlantic forests are not numerous nor of sufficient interest to be specified. They are such as Ampelopsis, Cornus stolonifera, and the like. The genus Shepherdia, however, is somewhat noteworthy. S. argentea, the Buffalo Berry, which seems most at home in the Northeastern Rocky Mountains, and which extends much beyond them in the same direction, along with its rela- tive Hlaagnus argentea, extends southward even to New Mexico, and westward to the Sierra forming that rim of the Great Basin; and it is accompanied by S. Canadensis, a characteristic shrub of the northern border of the Atlantic forest. The third species of the genus is peculiar to Southern Nevada.
Of the shrubs which traverse the continent and completely enter the Pacific forest the following are the principal:
Rhus glabra. Betula glandulosa.
Rhus aromatica. Alnus incana ?
Neillia opulifolia. Corylus rostrata.
Pyrus sambucifolia. Juniperus communis. Symphoricarpus racemosus. Juniperus sabina ?
Symphoricarpus occidentalis. Arctostaphylos Uva-Urst, if we con-- Lonicera involucrata. descend to one so low.
Sambucus racemosus (pubens).
The last three and the Sambucus are of the Old World, North Asiatic as well as European. They are all of northern range, and are there
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 19
somewhat continuous across the continent, although extending well southward along the mountains.
A full analysis of the herbaceous vegetation would run too far into details. We can mention only the peculiar types and some of the genera which are characteristically prominent.
The three genera (each of a single species) which are wholly restricted to the Rocky Mountains are Chionophila, which is strictly alpine, and has been already mentioned as such, and Leucampyx, an Anthemideous Composita (both of southern habitat), and Orogenia, S. Watson, a little Umbelliferous plant, with habit of Hrigenia, but too little known to speak of.
Synthyris, a Scrophulariaceous genus of seven species, is a character- istic but not quite a peculiar type, one of the seven species being of more western habitat, and one on the eastern verge of the Atlantic region.
Hesperochiron of S. Watson is a peculiar Hydrophyllaceous type, but both species occur also in the Sierra Nevada.
Lewisia is a most characteristic and almost peculiar genus; but the original species has been found even in California, and a second one oc- eurs on the southwestern rim of the Great Basin.
Townsendia is a highly characteristic genus, but some species belong to the alpine regions above and some to the dry plains below the forest region, and a few have a more western range.
Sidalcea candida is a restricted species of a genus peculiar to our and @ more western region.
Glycosma, Cynapium of Nuttall (now in Ligusticum), Camassia, Cory- dalis Caseana, Parnassia fimbriata, Gaultheria Myrsinites, and the con- siderable genera Wyethia and Helianthella, are in very similar case.
Calochortus is a most characteristic type of numerous species, some of the Rocky Mountains, more of them Californian, and a few Mexican.
Adenocaulon bicolor (of a peculiar genus, which is also both Eastern Asiatic and Chilian) is rather a western coast plant, which has traversed the Rocky Mountains at the north, even to Lake Superior.
Frasera, a marked and wholly North American genus, has given one species to the Atlantic forest, and shared two or three with the western region.
But the characteristic features of the Rocky Mountain herbaceous vegetation in the region specified, taken as a whole and in reference to abundance both of forms and of individuals, are imparted by the follow- ing genera, which have assumed their maximum development in and west of these mountains, and are mainly if not quite peculiar to North America.
Gilia, Collomia, Phlox, and Polemonium, of the order Polemoniacee.
Pentstemon, Castilleia, and Mimulus, of the order Scrophulariacee ; and _ Pedicularis here takes its principal American development in the higher regions.
20 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [| Vol. VY.
Phacelia in Hydrophyllacec, but most of the species are below the for- est district and of westward range.
Eriogonum of Polygonacee, of which the same is to be said, although a few species are conspicuous in the wooded region. .
Composite are very prominent, as they are throughout North America, and the genus Aplopappus might be added to the foregoing; but the most characteristic genera are not in the wooded region. ‘There, too, the species of Solidago and of Aster are less numerous than at the Hast, and Hrigeron is more prominent than Aster.
The number of species of Astragalus in the Rocky Mountain and more western districts is inferior only to those of Asia, but they mostly affect. the unwooded plains.
Peculiar to and conspicuous in the cooler wooded region are the two beautiful long-spurred species of Aquilegia, A. eerulea and A. chrysantha, the former alpestrine, the latter at lower elevations, neither found north of Colorado.
A few of the Rocky Mountain wooded-region shrubs occur on the higher mountains and ravines of the Great Basin, probably more of them than are yet recorded. Of additional species only two come to mind, and both are peculiar. They are—
Shepherdia rotundifolia of Parry, in the mountains of Southern Utah.
Peraphyllum ramosissimum, Nutt., a peculiar Pomaceous genus, along the western rim of the Great Basin.
A few other higher-mountain species of Ceanothus come in from Cali- fornia, as to various herbs; but we call to mind no characteristic species of the basin which belong unequivocally to the forest district.
II.—WoopLEss REGIONS BELOW FOREST.
These may be distinguished into the lower mountain slopes, the west- ern arid district, of which the so-called Great Basin is the center and the exemplar, and the less arid, unbroken plains east of the proper Rocky Mountains.
1. The Lower Rocky Mountain Slopes, including the “ parks,” so called, of Colorado and valleys which are not condemned to a saline vegetation, partake of the growth above and helow, but they have a good number of characteristic plants. The prevalent characteristic shrubs are largely Rosaceous. They are: 7
Cercocarpus parvifolius, along with CO. ledifolius when that is not reck- oned among the trees; the former a species which is even more common on all Californian foot-hills. These districts are the headquarters of this peculiar genus, although the latter was founded on a Mexican species.
Cowania Mexicana, which is likewise Mexican, as the name intimates.
Purshia tridentata, which extends much farther north than the others, but not ascending above the base of the mountains.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 21
Spirea discolor, which in its various forms flourishes under exceed- ingly different altitudes.
Spirea Millefolium, which is quite peculiar to the Gréat Basin.
Spirea cespitosa should be added, although it spreads in mats over the face of rocks, concealing its trunk, instead of rising into the air.
Coleogyne ramosissima, a highly peculiar genus of a single species, found only on the southern border of the Great Basin.
Prunus Andersonii, of the Amygdaleous type, restricted to its south- western rim.
Hardly elsewhere is such an assemblage to be found. Of other shrubs, Ceanothus velutinus and Ribes cerewm are the most widespread and abun- dant. One species of Hphedra extends along the mountains almost to the northern border of the Great Basin, and two or three more are among the characteristic shrubs of the region south of it.
As to herbs, the genera and the groups mentioned above as predomi- nant ata greater elevation (especially Gilia, Pentstemon, Phacelia, and Eriogonum) still play a prominent part. <Astragali become more numer- ous, as also do white-flowered species of Ginothera,and Helianthoideous, Helenioideous, and Senecionoideous Composite are conspicuous, yet not more so than in other parts of North America. Few Composit are peculiar tothis zone, and few genera are peculiar to the Rocky Mount- ain region as distinguished from the Californian. The more character- istic genera of the whole region may be adverted to in another connec- tion.
2. The arid or desert interior district, namely, that between the Rocky Mountains and the Sierra Nevada, the central part of which is the Great Basin proper, with no exterior drainage, but which also extends far north between the Rocky Mountains and the Cascades, and is there drained by the Columbia River, and far south over the district through which flow the waters of Rio Colorado and the Gila, with also an exten- Sive eastern outlier between the Wahsatch and the Colorado Rocky Mountains, and, as well, north of the Uintas, drained by the Green River, the main and farthest source of the Colorado, where an arid woodless tract, with all the features of the Great Basin, broadly intersects the wooded Rocky Mountain ranges. The mountains which traverse and diversify these deserts are thought to occupy about half the area, and al- though many of them appear to be as bare as the intervening valleys, yet their varied surface and exposure and the condensation of moisture which they compel, even from an unwilling air, nourish a different veg- etation, consisting of a larger number of species. This having already been noted, only the botany of the valleys and plains is under present consideration.
The region, in a general botanical view, is one of undershrubbiness ; and the prevalent growth is composed of Artemisias, Chenopods, and lig- nescent small-flowered Composite. It cannot be better described than
22 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
in the terms employed by Mr. Watson in King’s Exploration (Rep. xxiv, xxv), which is here accordingly cited:
“No portion of this whole district, however desert in repute and in fact, is destitute of some amount of vegetation even in the driest seasons, excepting only the alkali flats, which are usually of quite limited extent. Even these have frequently a scattered growth of Sarcobatus or Halos- tachys, surmounting isolated hillocks of drifted sand, compacted by their roots and buried branches.
“This vegetation, covering alike the valley plains, the graded incline of the mesas, the rounded foot-hills, and the mountain slopes, possesses a monotonous sameness of aspect, and is characterized mainly by the absence of trees, by the want of a grassy-green sward, the wide distribu- tion of a few low shrubs or half-shrubby plants, to the apparent exclu- sion of nearly all other growth, aud by the universally prevalent gray or dull olive color of the herbage. * * * The turfing ‘ Buffalo’ or ‘Grama’ Grasses, which make the plains east of the Rocky Mountains a vast pasture for the bison, deer, and antelope, are here unknown. There are, indeed, various other species more or less abundant in localities, but always growing in sparsely scattered tutts and dying away with the early summer heats, or to be then found only in favored spots in the mountain cafions. Two or three species that may be said to mat into a sward are confined to alkaline meadows, and are nearly worthless for pasturage.
‘Of the more predominant species which form the mass of the shrubby and perennial vegetation of the entire region, some are confined almost wholly to the more saline localities. Of these the Halostachys occiden- talis is an exclusively alkaline shrub, growing where almost no other plant will. Much more widely distributed and abundant is the Sarcoba- tus vermiculatus, found nearly everywhere in the lower valleys where there is a decided amount of alkali, but rarely extending much beyond such limits. The more frequent plants accompanying these are Salicor- nia herbacea and several species of Suceda, and other mostly Chenopodia- ceous plants, and, if there are grasses at all, Brizopyrum spicatum and Spartina gracilis.
‘On the somewhat less alkaline and drier portion of the valleys are found in frequent abundance Atriplex confertifolia and canescens, or the nearly as common Grayia polygaloides, and rather less abundantly Artemisia spinescens, Eurotia lanata, and [Kochia prostrata. Sometimes mingled with them, but, wholly free from alkaline preferences, and beyond their range usurping entire predominance, is the ‘ Everlasting Sage Brush,’ the Artemisia tridentata. This is by far the most prevalent of all species, covering valleys and foot-hills in broad stretches further _ than the eye can reach, the growth never so dense as to seriously obstruet the way, but very uniform over large surfaces, very rarely reaching the saddle-height of a mule, and ordinarily but half that altitude.
‘The ‘ Broom Sage’ Bigelovia graveolens occurs in considerable abun-
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 23
dance along the dry valleys, often accompanied by Tetradymia canescens ; but upon the gravelly foot-hills the smaller Bigelovia Douglasii is much more frequent.”
One or two names are changed in copying so’ as to conform to the more recent nomenclature. Hurotia lanata, though it happens not to come into the above extract, is among the commonest of these plants, and is one of the widestinrange. Some Astragali, various Hriogona and Gilie, also several Phacelie and CGinothere, would be next in promi- nence, the Hriogona much the most so. But the peculiarity of the basin flora lies as much in the absence of other genera which charac- terize adjacent districts as in the ubiquity of those which have been mentioned.
The genera peculiar, or nearly so, to the Great Basin proper and its borders are chiefly—
Physaria, a genus which was confounded on mere habit with Vesicaria, belonging to the foot-hills rather than to the valleys, the principal species extending around the whole limits of the region, a peculiar one at the north and another at the south,
Platyspermum, Hook., a little Cruciferous: annual of the western border.
Purshia, DC., a Rosaceous shrub, already mentioned.
Tricardia and Conanthus, of 8S. Watson, Hydrophylaceous herbs, the latter close to Nama, the former a peculiar genus.
Oryctes, Watson, a rather obscure Solanaceous herb of Western Nevada.
Nitrophila, Watson, an Amarantaceous herb of alkaline soil.
Grayia, Hook., a Chenopodiaceous undershrub, already enumerated as one of the most characteristic of the desert plants. (Sarcotatus would go with it, except that it crosses the Rocky Mountains and abounds on the upper waters of the Missouri, where it was first known, being the Pulpy Thorn of Lewis and Clark.)
Hermidium, Watson, a Nyctagineous perennial of the western edge of the basin, intermediate between Bougainvillea and Mirabilis.
Oxytheca, Nutt., an offshoot of the great genus Hriogonum.
Tetradymia, DC., characteristic shrubby Senecioneous Composite of two or three species, which slightly overpass the borders of the basin.
Glyptopleura, Eaton, of two species, and Anisocoma, Gray, of one, de- pressed Cichoraceous annuals or biennials.
Chetadelpha, Blepharipappus, and Rigiopappus, each of a single species, and Psathyrotes of two, southern in range, also Composite.
There is, besides, Caulanthus of S. Watson, of two or three very char- acteristic desert species, but some Californian, and the genus is only artificially distinguished from Streptanthus, species of which reach the Pacific coast on the one hand and Missouri to Texas on the other.
Eremochloe, S. Watson, is @ peculiar genus of grasses, one species pe- culiar to the basin, another to the southeastern part of New Mexico.
24 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol. VI.
The arid region south of the Great Basin we propose only in a gen- eral way to refer to. It is one in which there is no barrier to the spread- ing of the same species from the Gulf of California to the Gulf of Mex- ico, and in which the plants of the basin region, of Southern California, of Texas, and of the Mexican plateau and mountains meet and mingle. This district has also a good number of peculiar genera of shrubs: Sal- azaria, in Labiate ; Holacantha, a spiny Simarubacea; Canotia, a rather doubtful Rutacea, to which might be added Thamnosma except that a second species is Texan; and Chilopsis, which extends into Mexico; among herbs, Canbya, a singular little Papaveracea; Petalonyx, in Loasaceze (also Cevallia, which extends both to Texas and Mexico); Hesperocallis, in Liliaceee ; Dithyrea, which has been joined to the Old World genus Biscutella ; Wislizena and Oxystylis, in Capparidacez ; Achyronychia, jn Mlecebracee ; and among Composite the genera Baileya, Riddellia, Hymenoclea, Hymenothrix; and here also are the headquarters of Lap- hamia and Perityle.
3. The eastern woodless plains.
If the arid district of the interior of the United States west of the east- ern Rocky Mountains is denominated the region of ‘“ Sage Brush” (7. ¢., of shrubby Artemisia and Chenopods), the mostly less arid, less saline, equally homogeneous, and even more extensive plains between the Rocky Mountains and the eastern forest region may be characterized as the region of Buffalo Grasses. Its full development is between latitude 35° and 45°, where it occupies an average of ten degrees of longitude. North of this it is narrowed or interrupted, and then merges into a district which is woodless from cold or from the nature of the soil, and at length arctic. Southward it is equally broad, and it trends westward and loses itself in the New Mexican plateau region, which has a certain character of its own, but in which the eastern forms of vegetation mingle first with those of the Rocky Mountains, with those of the Mexican plateau, and at length with those which prevail in the Great Basin.
The whole region rises very gradually westward and abuts against the mountains at an elevation of, for the most part, fully 5,000 feet. The annual rainfall on its eastern border is from 24 to 32 inches, tolerably well distributed; in its western part 14 to 16 inches. Upon the climatie characteristics, topography, &c., which have been well presented in various reports and summaries, especially in those published by Dr. Hayden, it is not our purpose to enter.
Nor have we here any special call to discuss the vexed “ prairie ques- tion,” viz, why it is that the eastern border of this broad district should be treeless, except along river banks, even where the annual rainfall is from 28 to 32 inches, and 8 to 10 inches of this in summer—as much rain as is in the upper part of Michigan and on the Canada shore of Lake Huron; also why prairies exist as deep bays or islands within the Atlan- tic forest region. Suffice it to note that the prairies east of the Missis-
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 25
sippi are mainly restricted to places having little or no more rainfall than that mentioned above; also that where annual fires have been pre vented, original prairie surfaces are changing into forests,* and that, generally, trees properly planted or raised from seed, with some nurs- ing at the start, are found to thrive along this whole border.
In view of this, and of the well-known habit of the Indians to burn over the dry vegetation of the plains and prairies in autumn, we had
thought it most probable “that the line of demarkation between our woods and our plains is not where it was drawn by nature”; that “ be- tween the ground which receives rain enough for forest and that which receives too little, there must be a debatable border, where compara- tively slight causes will turn the balance either way,” and where “ dif- ference in soil and exposure will tell decisively.” And along this bor- der, annual burnings, for the purpose of increasing and improving buf- falo feed, practiced for hundreds of years by our nomade predecessors, may have had a very marked effect in carrying this woodless district farther eastward than it otherwise might have reached.t
Along with this,a more hypothetical cause may be assigned, which, if valid, will help in other explanations. That natural rain-gauge, the Great Salt Lake in Utah, informs us that the rainfall is now increasing over the western border of the region under consideration. We know what the maximum height of the water was very long ago; but we know not the minimum. Itis not improbable that this era of increasing moist- ure is of no recent commencement, but has supervened on an earlier one of greater dryness than the present, and that this affected the great plains east, as well as the great basin west, of the interposed Rocky Mountains. In that case districts may now bear forest, under man’s care, which would have been incapable of it before this cycle commenced or had attained the present condition.
The western portion of these plains is not only drier, but in some parts alkaline, or with other characters of soil uncongenial to forage grasses, especially at the north, where there are only two inches of rain in the three summer and no more in the three winter months. A good deal of the southern part gets about four inches of summer rain, but only half as much in winter. In some parts, accordingly, the characteristic vegetation of the ultramontane plateau intrudes. The Pulpy Thorn, Sarcobatus, and its Chenopodeous associates are largely developed on the Upper Missouri waters, accompanied by a peculiar Sage-Brush, Arte- mesia cana, While the A. tridentata is rather rarely established on this side of the mountains.
We have termed this district the region of Buffalo Grass. The grasses form such an inconspicuous and unimportant a feature in the interior arid region that it has not been worth while to mention them, and even on the mountains, except in the alpine region, they are of small account.
*Vide Prof. C. A. White, in Amer. Jour. Sci., Oct., 1878. +See Forest Geography and Archeology, in Amer. Jour. Sci., 1878, Ser. 3, xvi, 94,—
26 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
On the eastern plains they are the characteristic feature. When we get beyond the eastern prairie border, the grasses of which are prevailingly eastern in character, we come upon plains which are generally covered with the very low and tufted grasses peculiar to the drier plains, which form, if not a sward, yet something which serves as a substitute for it, not green, except in early spring, but of a dull grayish hue, and the characteristic species usually rising only a hand-breadth above the sur- face. These are the Buffalo Grasses or Bunch Grasses, which have nourished hordes of bison and flocks of antelopes down to a few years ago, and which are now the capital of the herdsmen or ranchmen, and the nutritious food of increasing numbers of domestic cattle.
The Buffalo Grass, par excellence, and by its abundance, is Buchloé dactyloides of Engelmann. This is a dicecious Chlorideous grass, the male and the comparatively scarce female plants of which were very naturally thought to be of quite different genera until their relation- ship was suspected and determined by Dr. Engelmann, and this apt name was applied to it.
Munroa squarrosa of Torrey (Crypsis squarrosa, Nutt.), another much depressed and peculiar Chlorideous grass, is next in importance. Both are wholly peculiar to this region.
Bouteloua, a Chiorideous genus of a more ordinary type, of several species, chiefly endemic to this region and to corresponding districts in Mexico, is the third in rank. These are the “ Grama” Grasses—a name which probably came from the Spanish. They are taller, of sparser growth, and make good forage.
Pleuraphis Jamesi, Torr., is a Buffalo Grass peculiar to the conineee part of the region, with se westward extension.
Vaseya comata, Gray, represents another peculiar genus; but the spe- cies extends to the Californian region.
Hriocoma cuspidata is the Bunch Grass of the very driest soils, and naturally extends across the Great Basin.
Sporobolus airoides, Torr., abounds over the whole length of the region and beyond it, in the more low and subsaline soils. It is accompanied by Beckmannia (also a North Asiatic grass), by Distichlis maritima, by one or two wide-spread species of Atropis, &c. The drier ground in many places bears species of Stipa and Aristida. Hordeum jubatum and the peculiar Hlymus Sitanion are characteristic grasses.
Of other dominant and more or less peculiar forms of vegetation—hav- ing chiefly in view the central tract—we should mention a great white- flowered Argemone (A. hispida, Gray); Stanleya, and the greater part of the known species of Vesicaria; Cleome integrifolia; the whole genus Callirrhoé; a Krameria; a Glycyrrhiza; the herbaceous Sophora sericea ; the principal development of the peculiar genus Petalostemon, and south- ward numerous species of Dalea (which go on increasing into Mexico); also of Psoralea ; most of the species of Gaura, several of Gnothera, and the peculiar genus Stenosiphon, allied to Gaura; a good number of Cac-
No.1] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA, 27
tacee (chiefly Opuntie and Mamillaric), increasing southward; a thick- rooted perennial Cucurbita (perennis), with some relatives southwest- ward; the species of Macheranthera, or biennial Asters; Aplopappus spinulosus and some other species; Bigelovia and Gutierrezia in charac- teristic forms ‘which are shared with the ultramontane arid district, and a great development of Senecionoid Composite, perhaps not exceed- _ ing the other parts of the United States, yet more conspicuous to the eye; the two species of Solanwm with prickly calyx closed over the fruit; Pentstemon in species equaled only by California; Hedeoma and Mo- narda; Leucocrinum, which, however, extends westward.
Besides those variously mentioned, a goodly number of genera are peculiar to this and the more western districts, which we need not here enumerate. Of absolutely peculiar genera, there is Selenia, in Cruciferae; Cristatella, in Capparidacee ; Museniwm, Polytenia, and Trepocarpus, in Umbelliferse ; Thelesperma (except for a Buenos Ayrean species), Engel- manna, Bradburia, Diaperia, &c., among Composite; Stephanomeria, Lygodesma and Troximon are very characteristic Cichoraceous genera, which also abound far westward.
The characteristics of the Rocky Mountain flora—whether taken as a broad whole or in its constituent geographical parts—are in no small degree negative. What this flora lacks is perhaps more remarkable than what it possesses. This will appear on a comparison of the vege- tation of the three great regions: the Atlantic naturally wooded region; the Central region, woodless except on mountains; the Pacific region, largely but not wholly wooded.
HF
COMPARISON. OF THE ATLANTIC, PACIFIC, AND ROCKY MOUNTAIN REGION FLORAS.
A full and eritical comparison would require a tabulation of the gen- era and species of the North American flora, and of their geographical distribution, and this would be a large and difficult undertaking.
Even the sketch of the principal or salient features, which we may here present, it is best to confine to the central belt, along which the three regions are particularly well defined, namely, to the United States north of the peninsula of Florida (which has considerable tropical vege- tation) and of Texas, leaving out of view the Texano-Arizonian region, which, with the adjacent parts of Mexico, has in general a vegetation of its own, and is not very distinctly separable into wooded and wood- less, or even into eastern, middle, and western, districts. The same is ti.e case, in a different way, in the country north of the United States boundary, as has been already explained.
The comparison attempted is, therefore, that of the flora of ‘the Atlantic States between the Gulf of St. Lawrence and the Gulf of Mexico, on the one hand, with that of California and Oregon and with
28 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [V¥ol.VI.
the broad district between them, stretching from the plains of Arkansas to Dakota on the east to the Sierra Nevada and Cascade Mountains on the west. Then the alpine vegetation, already treated of, is left out of view, except in the case of endemic genera or forms not belonging to to the arectic-alpine flora. And itmust be kept in mind that the eastern slopes and outliers of the Sierra and its continuation, below the wooded portions, belong to the Great Basin or to the region reckoned with it. So we do not reckon Pinus monophylla, nor Chilopsis saligna, nor Leuco- crinum, and the like, as common to the Great Basin and the Pacific floras, but as pertaining to the former only; and generally we do not take account of species which merely overpass the border of the region they belong to. For example, we should not reckon Anemone Nuttal- liana, nor Dalea alopecuroides, nor Collinsia parviflora, and hardly Rubus Nutkanus as constituents of the Atlantic United States flora. Such limitations heighten the contrast between the compared floras, but render the comparison more manageable and effective, and also, as to the broad outlines, really more faithful to nature than they would be if the materials were indiscriminately collected from the descriptive books and every denizen of the frontiers regarded as a true citizen.
All naturalized plants and weeds of cultivation are, of course, neg- lected, including such as may be of American origin but which have accompanied man, even the aborigines of the country, almost everywhere. They belong to no particular flora, or at least are not characteristic of any.
The natural orders may be taken up seriatim.
RANUNCULACEZ.—Are represented on the Atlantic side by eighteen genera, on the Pacific by fourteen, in the intermediate region (the Rocky Mountain flora in the broadest sense) by twelve. The species are in nearly the same relative proportion, and a considerable number are com- mon even to all three floras, the most striking case of this being that of Clematis (Atragene) verticillaris. All the generaof the Rocky Mountain flora (if we except Crossosoma) areamphigean.* Of such genera, Paonia is peculiar to the Pacific, and Hepatica (if ranked as a genus) only to the Atlantic flora. The peculiar genera are Trautvetteria, Atlantic and Pacific; Hydrastis and Xanthorrhiza, wholly Alleghanian; and Cros- sosoma of California, a genus of dubious affinity, but probably nearest Peonia, in two species, one which belongs to the Arizonian district. The species of Delphiniwm increase from the Atlantic westward, and are remarkably prominent in California.
MAGNOLIACEZ.—Of three genera and eleven species in the Atlantic flora; are wholly absent from the westward floras.
ANONACE#.—Have a peculiar genus (the so-called Papaw) in the Atlantic flora, but nothing to the west of it.
* This is the most convenient designation of the genera indigenous to Europe and Northern Asia as well as to America.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 29
MENISPERMACE 41.—Of three genera and as many species in the Atlantic flora; are equally wanting westward.
BERBERIDACH 4.—This is a marked family in North America. The amphigzan genus Gerberis has genuine Atlantic and one (southern) Rocky Mountain species ; the western mountains have a characteristic and common low Mahonia (and another on the southern border); and there are two or three more on the Pacific side. Of herbaceous types the whole central region has none; the Pacific coast has Vancouveria and Achlys, peculiar genera of single’ species; the Atlantic has those four special genera, Caulophyllum, Diphylleia, Jeffersonia, and Podophyllum peculiar to it and to Northeastern Asia, of single species to each conti- nent.
NYMPH HACE ai.—Of the typical genera, Nymphea is represented only in the Atlantic flora and by two peculiar species (with others in Florida and Texas), and Nuphar by three species ; a peculiar Nuphar belongs to- the two western floras. Nelumbium has only an Atlantic species, which even reaches to the West Indies. Brasenia, that genus and single spe- cies of wonderful distribution, is common on the eastern and not very rare on the western coast. Cabomba is peculiarly Atlantic.
SARRACENIACE &.—This wholly American order of Pitcher-plants has its leading genus of six species confined to the Atlantic border ; a single curious representative, Darlingtonia, on the mountains of California; the third genus is on a mountain in Guiana.
PAPAVERACE A.— This small order, the typical genus of which is rep- resented in America only by an arctic-alpine species, has its largest and most remarkable generic diversification in North America, and in the belt of country now under observation, partly on the Atlantic yet more strikingly on the Pacific side. But, except for an Argemone which is very conspicuous over the great plains, and the alpine Papaver, spar- ingly met with on the highest peaks, the order is absent from the Rocky Mountain flora in general. No European type is indigenous to Eastern North America, and only one of the American is Japano-Asiatic, viz, Stylophorum, of course on the Atlantic side. The other Atlantic genus is Sanguinaria, which has no fellow. But California has a species of the European genus Meconopsis and the following endemic genera: Romneya of Southern California, with a large poppy-like flower; Arctomecon, poppy-like, except in its stigmas and the anomaly of persistent petals ; Canbya, a curious little plant with the same anomaly (the last two really belonging to the Arizonian border of the interior desert region, although within California) ; Platystigma, including Meconella ; Platystemon, with gynecium singularly separating into its constituent carpels, so as to simulate a Ranunculaceous plant; Dendromecon, a shrub in an otherwise herbaceous family; and Hschscholtzia, the only genus which extends into the Great Basin, and the singular characters of which are familar from the forms in common cultivation; add Hunnemannia from the Northern Mexican plateau. Next to the Sequoias, perhaps, these Papa- veracex form the most characteristic note of the Californian flora,
30 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VL
FUMARIACEZ.—Three genera, of which only the larger one, Corydalis, is amphigean. Its species are of Hastern Asiatic rather than European types and relationship. C. aurea and its kindred forms, rather than species extend across the whole continent and to Japan; the striking species described as C. Caseana, of the western Rocky Mountains to the Sierra, appears to break into analogous forms which have recently been taken for species. Dicentra, peculiar to North America and the Japano- Himalayan floras, has perhaps a majority of American species. They belong wholly to wooded districts. One species crosses the whole con- tinent along the northern border of our belt; in another case Pacific and Atlantic species hardly at all differ; the three or four others are peculiar. Adlumia, the remaining genus, is of a single Atlantic species.
CRUCIFER4.—For an order of over 170 genera and more than 2,200 species, North America, in her about 40 indigenous genera, none of over two dozen species, cannot be said to have a large share; and the exclusion of Arctic alpine forms reduces the number considerably. The Atlantic Cruciferee are almost all European in type; Leavenworthia and Warea are the only peculiar genera. The eastern border of the plains has a, local genus, Selenia, and there begin the characteristic genera Streptanthus and Stanleya, and species of Vesicaria multiply southward ; the Rocky Mountains exhibit no characteristic type, unless itis Physaria, but the arid region beyond begins to share with California in the abun- dance of Lepidiwm, and in the several endemic genera, of which Thysano- carpus is the most characteristic. Itis the Arizonian region that furnishes _the American representatives of the Old Word genus Biscutella, the Dithyrea of Harvey.
CAPPARIDACEA.—Within the limits specified North America has no Capparee, but all the genera of Cleomec except two are indigenous and the greater part of them peculiar to it—all in the warmer parts, the number of species and types increasing southwestward, and extending into Mexico. The peculiar types, Cristatella, Cleomella (of several spe- cies), Wislizenia, and Oxystylis, are characteristic of the southern part of the central region.
RESEDACEZ we exclude, believing Oligomeris subulata to have been a Spanish importation.
CISTACE.—Two of the four genera of this more conspicuously ori- ental order, Hudsonia and Lechea, are peculiar to the Atlantic States, to which also three species of Helianthemum are indigenous, and there is one species on the coast of California. The order is wanting to the whole intervening portion of the continent.
VIOLACE#.—In species of Viola North America is as rich as the Old World, and the Pacific flora as rich as the Atlantic and with greater diver- sity of type; a few species common to each, but most of them peculiar. The central flora has hardly any except in the alpestrine region, and these few and of wide-spread species. A Mexican Jonidium reaches Arkansas and Arizona.
No.1.| GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 31
POLYGALACEAi.—Represented by Polygala. The Atlantic flora is rich in species, all of them peculiar; the Pacific flora has only two, of a peculiar type. The Texano-Arizonian region has several, some of them Mexican, but from both the mountains and valleys of our belt the genus and the order are nearly absent.
KRAMERIACEZ.—Should be separately reckoned, whatever view be taken of the affinity of the warm-American (chiefly Mexican) genus Krameria. One species reaches the plains of Arkansas, and has obtained a lodgment on the coast of Florida; two or three more extend along the Mexican frontier, but hardly infringe upon the region under consid- eration.
FRANKENIACE &.—Of a single genus, of warm temperate and subtrop- ical coasts; has a Californian and Arizonian species; no Atlantic repre- sentative, but there is a quite peculiar species at the southeastern base of the Rocky Mountains.
CARYOPHYLLACEZ.—The Silenece are feebly represented (by Silene only) in the Atlantic flora, yet by peculiar species; are nearly wanting from the Great Plains, scanty in the Rocky Mountains, but of increas- ing number and diversity as the Pacific flora is approached. The Al- sine, moderately numerous, call for no remark, except for the increased number of species of Arenaria in the interior flora, most of thenr peculiar. Stipulicida is of a single strictly Atlantic species.
TLLECEBRACE2.—Nowhere very numerous, but most of the species and genera in the Old World. Paronychia is represented in the Atlantic flora; also in that of the plains and the eastern part of the Rocky Mountains. Anychia and Siphonychia are peculiar to the Atlantic flora; Pentacena to that of the Pacific coast,extending to Chili. Achyronychia, a remarkable genus, of one species, belongs to the Arizonian rather than the California flora.
PORTULACACAA.—This may be regarded as an American order, al- though the Purslane has accompanied man all over the world. The single species of Montia has an immensely wide distribution over the cool parts of the world. One of Claytonia and several of Calandrinia are Australian, and two small genera are South African. So, as relates to distribution, it is a very suggestive order. The Atlantic States have only the two earliest known species of Claytonia and a Talinum; New Mexico has a peculiar genus (TZalinopsis), too like an African one; the Rocky Mountain region has the characteristic and remarkable genus Lewisia, and more species of Claytonia, &c.; Spraguea and Calyptridium are peculiar to the whole country west of the Rocky Mountains proper ; Calandrinie are all western; and the Pacific flora contains most of the species of Claytonia.
ELATINACE&.—Two of our three species of Hlatine occur in the At- lantic, Rocky Mountain, and Pacific floras; one is restricted to the latter. The Texan Bergia very sparingly occurs in the Great Basin and on the Pacific coast.
32 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
HYPERICACE &.—Represented by three genera, of which the two small ones, Ascyrum and Hlodes, are peculiar to the Atlantic flora (except European relatives of the latter), which is rich in endemic species of Hypericum; the Pacific flora has three or four endemic species of the latter, the intervening region nothing of the order.
TERNSTRGMIACH 4.—This Hastern American and Eastern Asian order is represented only east of the Alleghanies, and by Stuartia, two species (the third in Japan); Gordonia, two species, and several hardly genuine species in tropical Asia.
MALVACE@.—This is one of the great and cosmopolitan orders, of which North America possesses a fair but not excessive representation. The species and forms here increase in number southwestward. Indige- nous plants only being regarded, no genus is common to North America and Europe excepting Lavatera, represented by two or three singular and mostly shrubby species of the Californian coast. Napca is strictly peculiar to the Atlantic flora, as also is the unique Sida Napea. Callir- rhoé is peculiar to the borders of the same district and the plains adja- cent. Sidalceais peculiar to the Rocky Mountain and Californian floras. Ingenhouzia (which is Thurberia) belongs the Western Arizonian flora.
Malvastrum and Spheeralcea (too near generically) are numerous in spe-
cies on the plains and through the valleys of the Rocky Mountain region.
Kosteletzkya is represented on the Atlantic coast, but most of the species.
are Mexican.
BoMBACEZ.—Fremontia Californica belongs wholly to the forest dis-
trict of the Sierra Nevada, and its only relative is Cheirostemon, the Hand-flower of Mexico.
TILIACEA.—Hxcepting one or two outlying plants on the southern borders, this order is represented only by the genus Tilia, in two species of the Atlantic States, which hardly cross the Mississippi.
Linacre ai.—Three or four Atlantic species of Linum, as many more on the plains or Rocky Mountains, one species from the plains to the Pa- cific coast, and the same is an Old World species, or nearly so; and, moreover, in California and Oregon an unique group of seven species (Hesperolinon), in which the carpels are reduced from five to three, or even two.
ZY GOPHYLLACE &.—Leaving out the species of Tribulus or Kallstre- mia and the Texano-Arizonian representatives, among which Fagonia Californica should be ranked, notwithstanding the specific name, only the Creosote Bush remains, Larrea Mexicana, a shrub of the Mexican plateau, which has passed into or near the southern border of our belt all along from Texas to California.
GERANIACE.—In the restricted sense, are few in North America, consisting only of a few species of Geranium; the eastern and western perennial ones different; a biennial species of a weedy character is seat- tered over the continent.
LIMNANTHE@.—Are exclusively North American; Limnanthes, of two-
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN PLORA. 33
or three species on the Pacific side, the reduced type Flerkea on the Atlantic side also; all wanting to the Rocky Mountain flora.
OXALIDEA.—A very few species of Ovalis, one peculiar to the east and one to the west, one to the east and middle, and the O. corniculata both east and west.
BALSAMINE Ai.—Two species of Impatiens in the Atlantic States; none farther westward.
RuvTAcEa.—Mainly a tropical and subtropical order and not largely American, it is only to be noted that the Rutew are represented along the southern border by Thamnosma, a Texan species of which reaches the southern Rocky Mountains, and another belongs only to the southern border of the Great Basin. Ptelea extends quite across the continent, whether in one or in three species is uncertain; and two species of Xan- thoxylum are restricted to the Atlantic border. COneoridium is a little Californian shrub which rather belongs to this order. The American Simarubacee are south of our range.
CYRILLEZ.—Two strictly Atlantic genera, one tropical American and a West Indian one, compose the group.
AQUIFOLIACE 4 are represented only in the Atlantic flora by a dozen species of lex and the peculiar monotypic genus Nemopanthes.
CELASTRACEZ.—The single Celastrus is restricted to the Atlantic flora, which has also two species of Huonymus; the Pacific coast has one. Pachystima is a genus of two species, one common through the mountains from the Pacific to the Rocky Mountains, the other extremely local in the Alleghanies of Virginia.
RHAMNACE Z.—Excluding the Texano-Arizonian forms and the sub- tropical of Florida, we are concerned only with Rhamnus and Frangula, one species of which crosses the continent northward, two Atlantic only, and two Pacific; Sageretia and Berchemia, each having one Atlantic coast species; and the great American genus Ceanothus. The original species and three others are restricted to the Atlantic flora; three are Mexican; but the rest, twenty or more species, belong to the Rocky Mountains, where there are few, and to the Pacific flora, where they are perhaps the most abundant and characteristic shrubs, forming a large part of the chaparral.
VITACE.—Ampelopsis belongs to the Atlantic flora, but reaches the southern Rocky Mountains. Vitis has eight or nine species in the same flora, and is therefore more developed here than in any other part of the temperate zone. California has one species; the Rocky Mountains and their outlying districts none at all.
SAPINDACE Zs. argely tropical, except that there is a Sapindus along the southern frontiers; are represented only by certain genera. Four species of Wseulus characterize the Atlantic flora; one, of a dif- ferent type, the Pacific flora; and there is none between. [ive species of Acer are peculiar to the Atlantic, two to the Pacific flora ; one occurs only in the western Rocky Mountains; one is common to the latter and
36GB
34 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol. VI.
to the Pacific flora. MNegundo, which is hardly distinct from Acer, has an Atlantic species extending to and through the Rocky Mountains; a second but closely related species takes its place in California. Staphy- lea, which affects only forest regions, has an Atlantic and a (local) Pacific species. Glossopetalon is peculiar to the intermediate dry region; the original species occurs on and beyond the southern borders of the Great Basin; a second one is on its northwestern border. Ungnadia of Texas is rather too far southwest to be well reckoned in the Atlantic forest flora, yet it belongs to it.
ANACARDIACE %.—Represented by the genus Rhus. The only species which extends across the continent is #. aromatica, in a peculiar western variety. &. glabra, the low Sumach, extends to and beyond the Rocky mountains. The common Sumach, the Poison Dogwood, and some others are wholly eastern, while Rhus Toxicodendron reaches the Rocky Mount-
-ains; on the Pacific side it is replaced by an equally poisonous and very similar species. Southern California has two other species of South American type. p
LEGUMINOS#.—This being one of the very largest orders in most parts of the world, only characteristic features can be noted. The At- lantic flora is rich in genera, but poor, comparatively, in species; the Pacific is very poor in genera, but several of the genera are very numer- ous in species. The intervening region-on the western side has the Cal- ifornian character. They may be referred to under the suborders.
PAPILIONACE Z.—The great preponderance of Pacific species is attrib- utable mainly to the great development of four genera, viz: Astragalus, Lupinus, Trifolium, and Hosackia. The latter is the only purely Ameri- can type of the four, though very near to the Old World genus Lotus, and, but for one species which has nearly reached the Atlantic seaboard, would be wholly western.
The only peculiar Pacific genus is Pickeringia, of a single species. There is no peculiar genus of the Rocky Mountain flora, Olneya being Arizonian. The exuberance of Atiantic genera is largely due to genera which are divided between the Eastern United States and Eastern Asia, such as Wistaria, Apios, Amphicarpcea, Lespedeza, Cladrastis, and to some exclusive genera, such as Baptisia, Robinia, Petalostemon ; also to the absence toward the Pacific of genera which the Atlantic States share with Mexico and South America, such as Tephrosia, Indigo- Sera, Sesbania, Stylosanthes, Desmodium (the largest Atlantic States genus), Hrythrina, Clitoria, Centrosema, Galactia, Rhynchosia. More- over, the botany of California should surrender its eleven species of Dalea, since they all properly belong to the Arizonian and Great Basin floras rather than to that of the Pacific region. It is a characteristic . genus of the Mexican plateau and of its extension northward. Astra- galus, feebly represented in the Atlantic States, and its appendage, Oxytropis, have their American headquarters in the plains and mount- ains of our interior region, under conditions not unlike those of Northern
No.1; GRAY AND TIOOKER ON TIE ROCKY MOUNTAIN FLORA. 35
_ and Central Asia, where a great majority of the rest of the Astragalee flourish. Amorpha is shared by the Atlantic and Pacific floras. Ther- mopsis, with three local Atlantic species, one in the Rocky Mountains and two in California, has also Eastern Asian species.
C HSALPINEA.—Hxcluding the Texano-Arizonian forms, the only Pacific representative is a single Cercis; the central region has none, except, perhaps, a Hoffmanseggia or two; while the Atlantic has a Oercis of its own, rising to the size of a forest tree, also stately trees in Gym- nocladus and Gleditschia (two species), and of herbs a few species of Cassia. .
MIMOSEZ are in nearly similar case. Not one is truly to be reckoned in the Pacific flora or in the Rocky Mountain flora within our proper bounds, though several representatives appear a little farther south; but Schrankia, a Mimosa, a Neptunia, and two or three species of Des- manthus (all herbaceous) come within our limits on the ultra-Mississip- pian plains and barely enter the Atlantic flora. The shrubby or arboreal Méimosece (Mimosa, Prosopis in its two forms, Acacia, &¢.) char- acterize the Texano-Mexican bordering district.
RosacEz.— This important order has very characteristic North American genera. ‘Unlike the preceding order, the western genera are more numerous than the eastern, and also about as numerous in species. Taken under their suborders or great groups—
CHRYSOBALANE &.—Are represented only on the Atlantic coast, and by a single Chrysobalanus, excluding, of course, the tropical one in Florida. -
AMYGDALEZ.—Occur in the Atlantic flora only under the true Pru- nus, Padus, Cerasus, and Lauro-cerasus sections, except that in Texas forms approaching Amygdalus occur. The Pacific flora has scanty rep- resentatives of the same types. The southern and western borders of the Great Basin are marked by two peculiar Amygdalus-like species, Prunus Andersonii, in which the exocarp falls from the stone in two valves like an almond, and P. fasciculata, on which Torrey founded a genus, Hmplectocladus. Then, the Pacific coast has the curious and unique genus Nuttallia, Torr. & Gray, which is regularly pluricarpellary.
The trne Rosacee have Spirwa in several types, Neillia, Rubus, Geum, Fragaria, Potentilla, Agrimonia, Poterium, and Rosa, in common over the continent, the species of Potentilla much increasing westward. Peculiar to the Atlantic flora are only Neviusa (of Japanese affinity), Gillenia, and Datlibarda ; to the Pacific flora, Chamebatia, which abounds over the western slope of the Sierra Nevada, and Adenostoma, which forms a large part of the chaparral or chamisal (the shrub is called “Ohamiso”) of the foot-hills and coast-ranges. Peculiar to the Rocky Mountain flora, mostly to the Great Basin and to its southward exten- sion into Mexico, are Coleogyne, a single and very local shrub of the desert, Cowania, Fallugia. Peculiar, or nearly so, to the two western regions are Oercocarpus (with one Mexican species) and the two poten-
?
36 BULLETIN UNITED STATES GEOLOGICAL SURVEY. — [Vol.V2.
tilliform genera or subgenera, Horkelia and Ivesia, the former of which might rather be ranked among the exclusively Pacific types. A single Acena is one of the Chilian forms which has reached California. Wald- steinia, on the Atlantic side, is an Old World type. j
PomE#&.—The amphigzan generaor groups, Crategus, Malus, Sorbus, Amelanchier, extend across the continent at the north, one Sorbus in the very same species; only Crategus on the Atlantic side displays a con- siderable number of species; and. the Adenorachis group is peculiar to the latter district. Heteromeles, of Asiatic type, is confined to the coast of California. Peraphyllum is a peculiar shrub of the western verge of — the Great Basin.
CALYCANTHACE &.—Are all North American, except the. single Ché- monanthus of China; two species of Calycanthus peculiar to the Atlantic flora, one to that.of California.
SAXIFRAGACEZ.—An order hardly inferior to. Rosacez in extent, in amount of diversification, and in wideness of distribution. Of the am- phigean types, headed by Saaxifraga, it is unnecessary to discourse, ex- cept to mention that noble and most peculiar Californian species S. peltata.. The peculiar North American genera are, on the Atlantic side, Sulli- vantia and Decumaria; of the Rocky Mountain flora, Jamesia, and far- ther south, Fendlera; of the Pacific flora, Leptarrhena, Tolmica, Bolan- dra, Sucksdorfia, Carpenteria ; of the Rocky Mountain and Pacific floras in,common, Tellima, Whipplea; of the Atlantic and Pacific floras, but — not in the intervening, Boykinia ; of all three floras, Heuchera ; of all three northward, with extension merely into Northeastern Asia, Tiar- ella and Mitella, also, with intervening species farther south, Philadelphus. Then, Astilbe, Hydrangea, and Itea are genera strictly divided’ between the Atlantic flora and that of Himalaya-Japan. In Lepuropetalon we have the rare case of a species peculiar to the Atlantic and the Chilian floras, with no known connection. The genus Ribes assumes its max- imum development and fullest diversification in North America and on its western borders. Even with the alpine species included, Saxifraga is comparatively weak in this country.
CRASSULACEZ.—The amphigean genera Tillea and Sedum are not largely represented in North America. A Mexican group, Echeveria, extends well north along the Pacific coast, but is wanting in the inte- rior. Diamorpha, an unique genus of a single species, allied to Sedum, is of the Atlantic flora. Penthorwm, equally peculiar, is of a single species, restricted to the Atlantic States and to China and Japan.
DROSERACE.Az.—Appear to be absent from the whole Rocky Mount- ains, except in the cool regions far north; the Pacific flora northward has the two common amphigzean species; the Atlantic flora has four pecu- — liar species, and also rejoices in Dionea.
HAMAMELIDEZ.—Ave divided between Atlantic North America, South Africa, and Asia (to which most of the genera and species belong); our single Hamamelis does not cross the Mississippi; the monotypic Fother-
No.1] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 37
gilla hardly crosses the Alleghanies; the single Liquidambar is equally of eastern range, though it extends into and through Mexico.
HALORAGE.—Are of small account. The amphigzean Hippuris and one or two of Myriophyllum extend across the continent northward; but Proserpinaca, of two species, is restricted to the Atlantic flora.
MELASTOMACE®.—Khewvia of the Atlantic flora alone represents this great typical order in a temperate climate.
LyTHRrAcni A.—Largely tropical or subtropical; two or three species of Ammannia and Lythrum are of wide distribution; and the Atlantic States have a Cuphea and a Neswa, Hastern South American types. The pecu- liar genus Didiplis is nearly an aquatic Ammannia.
ONAGRACEAI.—A largely American order. Zpilobiwm, a cosmopoli- tan genus, is most diversified in the Pacific flora. Clarkia, Boisduvalia, Dulobus, Bucharidium, and Heterogaura are restricted to it; Zauschneria, Gayophytwm, and the principal wealth of the great genus @nothera, to the Rocky Mountain and Pacific region; Gauwra and Stenosiphon mainly to the great plains east and southeast of the Rocky Mountains. Zud- wigia and the diurnal yellow-flowered Gnotherc, with clavate capsules, are Atlantic types. Godetia is one of the most characteristic of Pacific- coast genera, but also Chilian.
LOASACE @.— Are wholly American, with the odd exception of a South African genus of a single species. It is wanting from the Atlantic flora, but well represented in the Rocky Mountain and Pacific floras by various species of Mentzelia. The most showy vespertine species, Jf. ornata and M. nuda, are very characteristic on the plains between the Mississippi and the Rocky Mountains. Hucnide and Petalonyx are Texano-Arizo- nian genera. ;
TURNERACEA.—Tropical plants; one or two species of Turnera on the southern borders of the Atlantic flora.
PASSIFLORACE 2.—Are equally unknown to the Rocky Mountain and Pacitic floras. A very few species of Passiflora are indigenous to the Atlantic States, one extending as far north as Ohio.
CUCURBITACE Z&.—Are few in this country, and from the interior re- gion within our proper Jimits they are absent. The true ELchinocystis is peculiar to the Atlantic States; two or three species of Megarrhiza char- acterize the Pacific flora ; perennial and tuberous rooted species of Cucur- vita belong to the plains east of the Rocky Mountains (C. perennis) and through drier Texano-Arizonian regions.
DATISCACEZ.—A _ single Datisea in California, far away from all its relatives.
CACTACE A.—Are abundant in and characteristic of the Rocky Mount- ain region, and still more of the Texano-Arizonian, as of the Mexican . plateau. Two species of Opuntia extend along the Atlantic coast to New England. Twenty-six species are enumerated in the Botany of Cali- fornia, but a majority of them belong to the Arizonian district.
FicoipE.a.—Are extremely few and uninteresting. The early natu-
38 BULLETIN UNITED STATES GEOLOGICAL SURVEY. — [Vol.V». ralization and great abundance of Mesembrianthemum on the coast of California is somewhat wonderful.
UMBELLIFER@.—This great order of over 150 genera is not notably large in North America. The number of genera in the Atlantic and the Pacific floras is about the same, but the species of the latter are much more numerous, and the interior region is equally well supplied. The largest western genera are Cymopterus and Peucedanum, the former peculiar to the region. Phellopterus, a plant of the northern Pacific sea- coast, is also on the coast of Japan.. Angelica Gmelini is common to the two, also to the mountains and the sea-shore of Northern New England. Cryptotenia of the Atlantic flora is identically the same in Japan. Os- morrhiza consists of two Atlantic species, two Rocky Mountain and Pa- cific, and one of Japan, all closely related. Orantzia lineata, a little plant of the Atlantic States seaboard, occurs on the border of Mexico and in South America, and again on the seaboard of Chili and Patago- nia, on the Falkland Islands, and even in New Zealand and Australia.
ARALIACE#.—Are few in North America, but interesting for distribu- tion. Apparently there are none at all in the whole Rocky Mountain re- gion, except one in Southern New Mexico. There are only two in the Pacific flora; one of them is very close to the Atlantic Aralia racemosa and is Californian; the other, Fatsia horrida, forms an undergrowth in the Coniferous woods of the coast farther north, and is also in the northern : part of Japan. The Atlantic flora contains Aralia spinosa, the A. race- mosa already mentioned, A. hispida, A. quinquefolia, the American Gin- seng, and A. trifolia. Nearly all of these have close representatives in the Northeastern Asian (and Himalayan) region and not elsewhere.
CoRNACE.—Are of equally interesting distribution. Ofthe ordinary Cornels, four Pacific species are thought to be distinct from the seven of the Atlantic flora, although the characters are not very well made out, and they meet more or less in the Rocky Mountains. Then, Cali-: fornia only has a species (C. sessilis), of the European and Japanese C. mas type. C. florida of the Atlantic flora hasa more showy represent- ative in C. Nuttallii of the Pacific forest, and less close relatives in East- ern Asia. The herbaceous C. Canadensis crosses the continent at the north, and in Japan meets the allied C. Suecica. Nyssa, of the Atlantie flora, has congeners in the mountains of Asia, while Garrya of the Pacifie flora has them in the Texano-Mexican region and the West Indies.
CAPRIFOLIACE@.—Of the amphigzean genera there is little to remark, except the considerable development of Viburnum in the Atlantic flora. in species strictly cognate if not sometimes identical with those of Japan; their absence from the Rocky Mountains, except well northward, where ‘two cross to the northwest coast; and the occurrence on the Pacific side of only one endemic species. Symphoricarpus, a wholly American genus, has one or two species common to all three floras, one or two peculiar to each, in the central region a peculiar Mexican type. Triostewm is con- fined to the Atlantic flora and to Northeastern Asia, with the Himalaya.
Wo..1.1 GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 39
RUBIACEa.—This vast order of over 300 genera and 4,000 species forms an insignificant feature in North America, and in the northern temperate zone throughout. But the poverty of the Rocky Mountain and the Pacific floras is eXtreme. There are some species of Galiwm in all, and Cephalanthus is on both sides of the continent and of south- ern extension. Besides, the Pacific flora has only the peculiar mono- typic genus Jelloggia, with no near relative in the northern hemisphere. The Atlantic flora nearly monopolizes the genuine species of Houstonia, and its specially characteristic genus is Mitchella, which is repeated in a very similar species in Japan.
VALERIANACE.—A small family, is here unimportant. The only peculiar genus is Plectritis of the Pacific coast and that of Chili.
Composit #.—No detailed analysis can be expected here of the dis- tribution of an order which is thought to make up one-tenth of flowering plants and which composes a still larger proportion of those of North America. Yet afew points may be brought to view, taking the tribes separately.
VERNONIACE&.—Are known only in the Atlantic region, the princi- pal genus, Vernonia, however, extending over the prairie border of the plains. Stokesia is one of those strictly peculiar genera of a single spe- cies with which the Atlantic flora abounds.
EUPATORIACE A.—This is almost an American tribe, the maximum in South America, the minimum in our Pacific Territory, which has only four or five species. But into the Rocky Mountains and the Great Basin extends, more largely than into the Pacific flora, the genus Brick- ellia, founded on an outlying species of the Atlantic flora, yet mainly a Texano-Mexican genus. But the Atlantic flora is better supplied, and with peculiar genera, viz, Sclerolepis, Trilisia, Carphephorus (the South California species is hardly congeneric), the fine and rather large genus Liatris, which, however, reaches nearly to the Rocky Mountains and into Mexico, and Auhnia, which is in the same case. Garberia of Flor- ida, taken from Liatris, is too southern to be properly counted. The great genus Hupatorium is also well represented on the Atlantic side, and here only is the northern extension, in a single species, of the huge South American genus Mikania.
ASTEROIDE .—Are eminently American, and in no other single dis- trict are they so numerous as in the belt across the continent which is under consideration. Aster, Solidago, and Bigelovia are the great genera; Aplopappus, Chrysopsis, Erigeron, and Townsendia are next in importance. About four-fifths of the Asters and Solidagos belong to the Atlantic flora, with some extension into the plains beyond, and there also are more species and forms (but fewer individuals) of Chirysopsis; the amphigzen genus Hrigeron has its fullest development and diversification in our west- ern regions; Aplopappus is divided between our Rocky Mountain flora (with southward extension and into that of the Pacific) and that of Chili. Townsendia and Bigelovia are the most characteristic genera of the whole
40 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VL
Rocky Mountain region, although a few species of the latter reach the Pacific, while the original one belongs to the Atlantic coast. Grindelia and Gutierrezia are equally characteristic over the plains and quite over tothe Pacific, and both are sparingly represented in extratropical South America. Lessingia, Corethrogyne, and Pentacheta are peculiarly Cali- fornian. Boltonia and the Bellis integrifolia are peculiarly Atlantic. Baccharis, with an immense development in South America and Mexico, has penetrated northward on both coasts to about latitude 41°, eastward in a single, westward in very few species.
INULOIDEZ.—Are sparingly represented in America, and mostly in the Gnaphalineous type. They are particularly few in the Atlantic flora, and increase in number and diversification westward.
HELIANTHOIDEZ.—On the contrary, are mostly American, and largely North American. Here are almost all the true species of Heli- anthus, the perennials mainly Atlantic, the annuals more western. The Atlantic flora is characterized by Silphiwn, Chrysogonum, Tetragonotheca, Echinacea, and the greater part of Rudbeckia and Coreopsis, and it alone has a Heliopsis ; the eastern plains have Thelesperma (more developed farther.south, and reproduced in Buenos Ayres!), Hngelmannia, most of Berlandiera, &c.; the Rocky Mountains, Balsamorrhiza, Wyethia, Helian- thella, &c., which they share with the Pacific flora; the latter repro- duces the Coreopsoid type in Leptosyne and Pugiopappus.
GALINSOGEZ and MApIEz.—Being exclusively American (and Ha- waiian), and more related to the following than to the preceding tribe, de- serve separate mention. Baldwinia and Marshallia are peculiar to the Atlantic flora; Blepharipappus to the Pacific. The rest’ are Madiew, and are specially characteristic of our Pacific flora—are peculiar to it, indeed, except for the two Hawaiian Island genera, for the extension of the common Madia into Chili, and for the eastward extension of some species into the plains. MMadia, Layia, and Hemizonia, in numerous spe- cies, many of them showy, are predominant Composite in California.
HELENIOIDEZ (including the groups assigned to this tribe by Ben- tham).—Are specially American, are few in the Atlantic flora (where the few representatives are all of western types), are more numerous and characteristic in and towards the Rocky Mountains, while beyond them, as well as south of them and on the Pacific coast, they attain their fullest development. We will not enumerate the numerous mostly endemic genera.
ANTHEMIDE @.—Chiefly of the Old World; would be most insignifi- cant in North America except for the number of naturalized weeds and for the remarkable development of species and individuals of Artemisia, especially of those which compase the Sage-brush on either side of the Rocky Mountains. These have already been spoken of. For anything — like this development, as well as of the Chenopodiacez, which accom- pany the Wormwoods, only corresponding parts of Northern Asia can be looked to.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 41
SENECIONIDE .—Somewhat equally distributed over the world; offer little for remark. There is no peculiar type in the Atlantic flora nor east of the Rocky Mountains, but beyond them Tetradymia and Psathy- votes are truly characteristic of the Great Basin; Raillardella (the rel- atives of which are only in the Sandwich or Hawaiian Islands) is pecu- liar to the high Sierra Nevada, and Luina to the Pacific coast ranges. Western North America is, morever, the headquarters of Arnica.
CYNAROIDE&.—Are restricted to Cnicus, of which the Atlantic States, the Rocky Mountains and their accessory western ranges, and the Pa- cific side of the continent have about an equal and a moderate number of species (more or less peculiar), and the showy Centawrea Americana, now well known in cultivation, which inhabits the plains of Arkansas and Texas.
MUTISIACE& (including all the Bilabiatiflore of De Candolle).—A ffect the southern hemisphere, but come into a temperate region both in North America and Asia. In the former most are of the Texano-Arizonian district—Leria, Trixis, Perezia—and are outliers of the Mexican flora; but one of the latter genus fairly reaches California, and the original Chaptalia is of the Atlantic Southern States.
CICHORACE, or the Liguliflorw.—A very moderate number of the sixty genera are indigenous to North America. Apogon, Krigia, and Cynthia are peculiar to the Atlantic flora or its borders, Purrhopappus to this and the nearer parts of Mexico, and Nabalus has only one extra- neous northwestern species; but the open western country nourishes the greater part of our representatives of this tribe. From the plains to the Pacific spreads the genus Troximon, accompanied by Lygodesmia and Stephanomeria, and even by Malacothrix ; Glyptopleura, Anisocoma, and mainly Calycoseris are peculiar types in the Great Basin ; and fifteen species of Malacothrix are peculiar, or nearly so, to the Pacific flora, which has also Rajinesquia, Apargidium, and Phalacroseris. The paucity of the large and difficult Old World genus Hieracium in America is a wonder and a relief to botanists.
LOBELIACE &.—Lobelia is essentially wanting from the Pacific and the Rocky Mountain floras, but well represented in that of the Atlantic. Instead, the Pacific flora is characterized by four peculiar genera, Downingia, Howellia (an aquatic plant of Oregon), Palmerella, and the curious Nemacladus. It has also a peculiar Lawrentia, which extends eastward to the Rocky Mountains, where it is the only representative of the family.
CAMPANULACE@.—Are not numerous; but Campanula has a few representatives in all three floras (in the interior only on the mountains) ; Specularia has fewer; and two genera of single species, Githopsis and Heterocodon, are peculiar to the Pacific flora.
ERICACE A:.—This important order needs to be considered under its suborders.
VACCINE A3.—In the northern hemisphere affect the eastern side of
42 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VI.
continents. The five species of Gaylussacia (Huckleberries), and the dozen or more eastern endemic species of Vaccinium, as also the peculiar genus Chiogenes, sparingly enter even the eastern part of the Mississippi Valley. Only amphigzan types occur in the Rocky Mount- ains and in the alpine or alpestrine region. The moister parts of the Pacific coast nourish two or three species of Vaccinium, but no other forms; yet all the Atlantic types, except Gaylussacia, occur again in Northeastern Asia.
ERICINE &.—In North America are not unequally divided between the Atlantic and Pacific floras; but the interior region has very few, not one peculiar, and none except upon high mountains or of equivalent northern range. The Pacific flora is remarkable for having an Arbutus and ten species of Arctostaphylos of the Mexican type, for its solitary Leucothoé far away from congeners, its shrubby Gaultheria, and its spe- cies of Bryanthus; also for the peculiar Ledum which it shares with the Northern Rocky Mountains. It has one peculiar genus, Cladothamnus. The specially Atlantic Ericineous genera are Hpigea (yet with a Japan- ese counterpart), Oxydendrum, Kalmia, Leiophyllum, and Elliottia, this shared with Japan. This flora is particularly rich in Andromedec of eight or nine types, and here alone in the temperate zone we find a Bejaria. Only the counterpart Asiatic region excels it in Rhododendron and Azalea; yet the Pacific flora has three or four fine representatives of these. Menziesia in one species oceurs over the breadth of the con- tinent at the north, adding a second species on the way; thence to Japan, where there are more.
PYROLINEZ (including Clethra as the type of a peculiar tribe).—The two species of the latter genus are characteristic in the Atlantic flora; they are not found west even of the Alleghanies, to which one of them is restricted. North America is the headquarters of Pyrola and the related genera, having, nearly all the known species; and the western floras possess their full share.
MoNnNoTROPEA.—Al|so are strikingly American, notwithstanding the wide distribution of the typical Monotropa from South America to Himalaya, and to Europe of Hypopitys. All the genera and species, except one in Himalaya, occur in North America, and all but the peculiar Atlantic genus Schweinitzia are in the Pacific flora, to which half the genera are peculiar.
LENNOACEA —A Mexican group of three genera, having the habit of Monotropec; has one genus, Pholisma, on the coast of California, and another very singular one, Ammobroma, Torr., beyond its borders at the head of the Gulf of California.
DIAPENSIACE A, upon which we have elsewhere dilated, consist of the arctic-alpine Diapensia Lapponica and a congener in Himalaya, of two monotypic genera in the Atlantic United States (Pyxidanthera and Galax), of another (Shortia) divided between the Alleghanies (where it is apparently verging to extinction) and Japan, of a related genus in the
ra
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 43-
latter country, and of another in Tibet. From our western floras it is totally absent.
PLUMBAGINACE &.—In this country very few, and confined to the sea- coasts; are not noteworthy.
PRIMULACEA.—Need little mention, most of the genera being amphi- gean and widely distributed over the country, although few in species, many of them alpine or alpestrine. The most peculiar genus, Dode- catheon, spans the continent in very various forms, which seem to be connected into one species. The true species of Lysimachia are only on the Atlantic side, and so mainly is the peculiar genius Steironema, although the commonest species extends northward to the Pacific.
SAPOTACE a@.—Tiis is one of several orders which, although mainly tropical, have temperate representatives in the Atlantic United States, where there are at Jeast three species of Bumelia.
EBENACE &.—Arein similar case. Diospyros Virginiana, our Persim- mon, extends north to latitude 41°, and barely crosses the Mississippi- A Texan species lies beyond our line. Westward the order is wanting.
STYRACACEA.—Are found on both sides of the continent, but not at all in the intermediate regions. The order is one of those that affect the eastern side of continents. Accordingly, the Atlantic flora has three genera (Symplocos, Halesia, Styrax) and eight species; the Pacifie flora only a single Styrazx.
OLEACE.A.—Avre fairly well represented in the Atlantic flora by six or seven species of Fraxvinus, a few of Forestiera, a Chionanthus, and an Osmanthus ; two species of I’raxinus are the sole representatives in the Pacific flora. The wide intervening region has none except a Frarinus, with simple leaves, on the southern border, where also flourish one or two species of Forestiera and of the Texano-Mexican genus Menodora.
APOCYNACE &.—The two species of Apocynum make a part of all three floras; the Pacitic has a peculiar genus, Cycladenia ; the Atlantic, a plant referred to the Northeastern Asian genus Trachelospermum, and Amsonia (which is also Japanese), the latter reaching the southern borders of . the Great Basin.
ASCLEPIADACE4—Most of Asclepias is North American, and the spe- cies, as to number, are not very unequally divided between the three floras, at least if New Mexico and Arizona be taken into the account. This southern frontier and the country beyond is rather rich in the order. The Pacific flora has three species nearly related to Asclepias; one of them is made the type of a peculiar genus, Schizonotus, the other two are re- ferred to the chiefly African genus Gomphocarpus. The Atlantic flora divides with that of the plains up to the Rocky Mountains the genera Acerates and Aselepiodora, with tropical parts of America the genus Enslenia, and is also rich in Gonolobus; and it monopolizes the genera Podostigma and Anantheriz.
LOGANIACE@.—As our species of Buddleia and the genus Hmorya belong to the Texano-Arizonian region, it may be said that this order
44 BULLETIN UNITED STATES GEOLOGICAL SURVEY. _ [Vol. VI
is here restricted tothe Atlantic flora. This divides Gelsemium with East- ern Asia, Spigelia and Polypremum with tropical America, Mitreola with both.
GENTIANACEZ.—The Gentians, generally most numerous in mount- ain districts, preponderate in our western floras; yet the Atlantic States do not lack species. The amphigzan genus Hrythrea is finely repre- sented in the Pacific flora and in the Texano-Arizonian region, sparingly in the Rocky Mountain region, while in the Atlantic States there is probably no indigenous species north and east of Arkansas. Mierocala has probably reached California from South America. Menyanthes tri- foliata is all around the northern part of the temperate zone. MM. crista- galli is one of the few plants which the Pacific flora shares with that of Japan. The two species of Limnanthemum are strictly Atlantic, and are connected with tropical species of the eastern side of the continent. Halenia is at the same time a high-northern and an Andean genus. Swertia is absent from the Atlantic side of the continent. As to the peculiarly American genera, the finest is Frasera, with one Atlantic spe- cies, and a few others both of the Rocky Mountains and of the Pacific side of the continent. Hustoma reaches from the Texano-Arizonian region just within our border over to the eastern border of the plains. Sabbatia, of thirteen species, Bartonia, and Obolaria are wholly peculiar to the Atlantic flora.
POLEMONIACEA.—Although not wholly absent from Europe and Northern Asia, compose a truly characteristic American order, and, al- though half the genera are Mexican and South American, at least nine- tenths of the species must belong to the United States. Of these, an equally large proportion adorn the western regions, whether the mount- ains, the valleys, or the plains, under the various forms of Gilia, Col- lomia, and Phlox. Yet, to the Atlantic States belong the herbaceous perennial species of the latter genus, which have longest been known to botanists.
HYDROPHYLLACEA.—This is more strictly an American, and even more predominantly a Western North American, order than the pre- ceding. A very large part of our species and forms inhabit the Rocky Mountain region, chiefly its plains and valleys, and fewest the At- lantic region. No genus is restricted to the latter, though into it only extends the southern Hydrolea; into the lower parts of the intermediate regions extends the mainly Texano-Mexican genus Nama ; to it belongs Conanthus, Tricardia, and essentially Lemmonia ; to it and to the Pacific flora belong Hmmenanthe, Hesperochiron, Eriodictyon ; to the Pacific flora alone belong Draperia and Romanzoffia.
BOBRAGINACE#%.—This is a larger order, and is found all over the world. The tribes or suborders other than the Borragee hardly come at all within our limits, excepting two or three species of Heliotropiwm, one of which is very characteristic of the plains east of the Rocky Mount- ains (viz, H. convolvulaceum, the Euploca of Nuttall, and it has also
No 1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 45
been found in the Great Basin), and excepting the Tiquilia section of Coldenia, which extends to the northwestern verge of the interior wood- less region. The genera and species are few in the Atlantic flora. Its only characteristic genus is Onosmodium ; the yellow-flowered and showy Tithosperma of the section Batschia it shares with the plains. The great genus of the whole Rocky Mountain flora, though shared with the Pa- _ cific, is Hritrichium ; the characteristic genus of the Pacifie flora, of which its neighbor takes a part, is Amsinckia. Mertensia has most of its spe- cies in the Rocky Mountains and their accessories, yet the finest of them is M, Virginica, peculiar. to the Atlantic States. Pectocarya may have been brought from Chili to California. Some peculiar genera of the Arizonian flora are hardly within, our scope. -CONVOLVULACEA:.—There are no peculiar genera in. North, America, and, nothing notable, in distribution. Phere, are many more Atlantic: ve Pacific species.
SoLANACE2:,—As to truly indigenous species, are few north and east of Texas, and, not, numerous through the western portions of the country. Physalis is the largest. genus. The only peculiar genera are Chamesa- racha and the very little known. Oryctes, neither of salient character, both of the interior region. Into the southern part of the Rocky Mount- ains. extend, from Mexico two,species or forms of the Potato type.
SCROPHULARIACE.E. —North America has 37 indigenous genera of this. very large. order, several of them numerous in species. They are fewest. in the Atlantic flora, which yet has some peculiar genera, and it is noteworthy that only one of them (Schwalbea) is of near affinity to: Japano-Himalayan types. Throughout, the types which are not distinct- ively American are rather European, Mimulus, however, being an ex- ception. Thus, in California there is a remarkable development of the: genus Antirrhinum. Of the several tribes, there is one which is particu- larly characteristic of the Atlantic flora, namely, that which contains. Gerardia (of over 20 species), and is augmented by Macranthera, Sey- meria, and Buchnera. Some species abound on the eastern part of the plains, but none reach the Rocky Mountains or appear in the country beyond them. Of genera which are sparingly represented in the At- lantic flora or near its borders, and are in fuller strength westward, the more characteristic are Collinsia, and the great genus Ventstemon, with about 4 species at the east and nearly 40 in the Pacific flora; Mimulus, with 3 Atlantic and at least 23 Pacific species; Synthyris; Castelleia, with 3 or 4 Atlantic and about 20 western species ; Orthocarpus with one species on the northeastern plains and 24 in the western floras, chietly on the Pacific side, while its relatiyes in Cordylanthus add halt as many more. So Began is, with only 2 Atlantic species, increases westward to over 20.
OROBANCHACEA.—The four North American genera are wholly dis- tinct from the European, and from the Asian also, except for an Eastern Asian species of Boschniakia. Here also, although two of the genera
A6 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
are wholly Atlantic and one is divided (Aphyllon), the Pacific species are more than twice the number of the Atlantic.
LENTIBULACE&.—Both Utricularia and Pinguicula are of good num- ber and diversity in the Atlantic flora, are nearly absent from the Rocky Mountain flora, and are very few on the Pacific side.
BiGNONIACE@.—For a mainly tropical order, are pretty well repre- sented in the Atlantic flora by four species belonging to three genera (and the most distinct genus, Catalpa, alsoin Japan and Northern China), but would be wholly absent from the western floras except for a Mexican shrub (Chilopsis) which reaches the southern borders of the Great Basin.
PEDALIACEZ.—Are sparingly represented in the Texano-Arizonian region, but probably are not indigenous to the north of it.
ACANTHACE Z.—An immense tropical and subtropical order, but prob- ably without a single representative in the Rocky Mountain or Pacific floras within our limits, yet with severalin the Texano-Arizonian district. But the Atlantic flora has an Hlytraria and Hygrophila, one or two. species of Calophanes, as many of Ruellia and of Dianthera, a Dicliptera, and a plant of a peculiar genus, Gatesia.
VERBENACE®.—Of the eleven genera enumerated in the flora of North America, only four are of such northern range as to come within our limits. Verbena and Iippia enter into all three floras. Callicarpa and Phryma are restricted to the Atlantic flora and to a solitary species. Both the latter are Eastern Asian, the Phryma in the same species.
LABIAT&.—A large and important order, but after excluding the naturalized plants and those which range south of the present survey, neither the American species nor the genera are particularly numerous, nor is their distribution such as to call for much remark. They are most conspicuous in the Pacific forest in the Rocky Mountain region, most diversified in genera in the Atlantic States. Of the North Ameri- can types, Physostegia, Lophanthus, Pycnanthenum, and Trichostema are common to both sides of the continent, the latter most largely on the Pa- cific; the latter numerously on the Atlantic side, with a single Californian species far away from its congeners. .The peculiar Atlantic genera are Isanthus, Cunila, Collinsonia, Oonradina, Ceranthera, Blephilia, Monarda (which extends into the Rocky Mountains), Brazoria, Macbridea, Synan- dra. The Pacific peculiar genera are only Monardella, Pogogyne, Acan- thomintha, Audibertia, the first and the last extending eastward to the Rocky Mountains in single species. Hedeoma is a remaining character- istic genus, with headquarters in the Texano-Mexican district, extending over the eastern plains, and one species to the Atlantic. The great genus Salvia is meager on both sides of the continent, almost absent from the interior, except on the eastern plains toward the south, but fairly numerous in species throughout the Texano-Arizonian region.
PLANTAGINACEA.—Are few in species. Plantago Patagonica, which abounds on the plains and on the Pacific coast southward, is very poly-
No. 1.1 GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 47
morphous and of immense geographical range. It is worth noting here that the other genus, Littorella, till now supposed to be wholly European, has been detected at three or four stations within and near the northern borders of the United States.
NYCTAGINACE@.—Are essentially absent from the Atlantie flora, abundant in the Texano-Arizonian; are represented by Oxybaphus on the plains east of the Rocky Mountains and by Abronia beyond them; also by Quamoclidion or Mirabilis with several-flowered calciform invo-
_Iuere. The Great Basin has a peculiar genus, Hermidiwm of S. Wat- son, allied to Bougainvillwa of South America, but herbaceous.
AMARANTACE Ai (weeds excluded).—Are chiefly of the Rocky Mount- ain region in its warmer and drier parts. Acnida, however, is more eastern.
_ CHENOPODIACE.—Are of similar distribution, but far more numer- ous and diverse. They are the most characteristic and abundant of the plants of the dry interior region, as has been elsewhere stated, and ‘they naturally extend into the Pacific flora more than into the Atlantic. Atriplex is the great genus. Grayia and Sarcobatus are the endemic shrubby genera. Spirostachys is of an extratropical South American type. Cycloloma and Suckleya are herbs peculiar to the eastern plains. PHYTOLACCACE&.—Are represented only in the Atlantic flora, and by asingle Phytolacca, Rivina belonging farther south. “POLYGONACE4@.—The genuine Polygonee on the Atlantic and Pacific sides by Polygonum and Rumex, and by Polygonella in the southern part of the former; and there are a few in the interior, where Rwmex venosus is a characteristic plant. But the most characteristic plants of the two western floras, and the most numerous in species, if not in individuals, are the Hriogonece. The genus Lriogonum, founded at the beginning of the century upon the single-known and still the only Atlantic species, now comprises nearly 100 species in our western floras, and the subsid- iary genera (Oxytheca, Centrostegia, Chorizanthe, Nemacaulis, Hollisteria, and Lastarreia, all mainly Californian, and three of them also Chilian) about three score more. Pterostegia, of California, proves to be most related to the arctic-alpine Kenigia. Another type is represented in the southern part of the Atlantic flora by the peculiar genus Brunnichia. PODOSTEMACEZ.—Aquatic plants of tropical or subtropical rivers, mostly of the southern hemisphere. A single Podostemon, on which the genus and order were founded, belongs to the Atlantic United States. Its congeners are all in Brazil, Madagascar, and India!
ARISTOLOCHIACE Ai.—Absent from the whole intermediate region, there are three species of Asarwm in the Atlantic and three others in the Pacific flora; three of Aristolochiain the former and one in the latter.
PIPERACEZ, tribe Saururee.—A Saururus in the Atlantic flora, the
only other one Chino-Japanese; a Houttuynia (if not a good genus, Anemiopsis) in California and thence to Mexico; its relatives also East African.
48 BULLETIN UNITED STATES GEOLOGICAL SURVEY. (Vou. VI.
LAURACEA.—Mainly tropical or subtropical all around the world, yet there are three genera in the Atlantic flora (one, Sassafras, a fine tree, and all of Asiatic affinities) and a peculiar one in California.
THYMEL ACE Z.—Most developed in the southern hemisphere. In North America is only Dirca, one species in the Atlantic flora, the other, very local, in the Californian.
ELZAGNACE.—Two of the three genera of this little order are North ~ American. The two species of Shepherdia nearly traverse the continent at the north, and a third species has been discovered on the southern rim of the Great Basin. An Eleagnus belongs to Rocky Mountain region.
LORANTHACEZ.—Are represented by two genera, allied to Viscum. Phoradendron is peculiar to America. The common species in some its of forms traverses the continent; another belongs to the Californian dis- trict. and adjacent parts; the others are more southern. Arceuthobium is amphigzan, of three or four American species, mostly Pacific or south- ern, one.sparingly represented in the Northern Atlantic States.
SANTALACE@.—Are most largely of the southern hemisphere. The © distribution of our four genera is interesting. Comandra, consists of. a European species, two North American ones, which traverse the conti- nent northward, and a fourth, which belongs mainly to the Rocky Mountain region southward. Buckleya consists of an Atlantic (Alle- ghanian) species and one in Japan; Darbya of a single and local Atlan- tic species, of some ambiguity, because the female plant is unknown; Pyrularia of an Alleghanian species and a Himalayan.
EUPHORBIACE&.—An immense order of 3,000 species and, at the least, 200 genera. The world-wide and prolific genus Huphorbia is very mod- erately represented in the Atlantic flora, sparingly in the Pacific, numer- ously in the drier parts of the intermediate country, especially south- ward. The other large and non-peculiar genera are mainly southern in
‘range. Peculiar genera are very few—Hremocarpus in the Pacific flora 5. Crotonopsis in the Atlantic. Of the Buxinew, there is Simmondsia on the Californian coast, of Wo near affinity; Pachysandra, in the Alleghanies,. which has a congener in Japan.
EMPETRACE @.—Have all three genera in the Atlantic flora, and not elsewhere—Hmpetrum alpine and northern ; Corema on the coast of the: United States, the other species on the opposite Atlantic coast in Ror- tugal; Ceratiola in the Southern Atlantic States.
CERATOPHYLLEA.—Probably of a single species, amphigzan, both Atlantic and Pacific.
URTICACEZ.—Taken in the large sense, may be referred to under their suborders.
UrtTIicEa.—Are few on either side of the continent, nearly absent | from the Rocky Mountains and Great Basin, an Urtica or two, and the: same of Parietaria ;-Hesperocnide is divided between California and the Hawaiian Islands; Laportea, of the Atlantic States, has its congeners. mainly in Hastern Asia. The solitary North American Pilea is confined. to the Atlantic States, and the same of Behmeria.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 49
ULMACEa.—There are four fine Elm trees in the Atlantic flora, and one farther southwest, also the Planera; none of these in the Rocky Mountain or the Pacific floras; Celtis, either a form of the common eastern or a peculiar species, extends into the Rocky Mountains and even to Oregon.
CANNABINE 4.—The common Hop of the Old World is indigenous in the Atlantic States and in the Rocky Mountains; the other species is Chino- Japanese.
Morria.—Morus rubra is of the Atlantic States, extending far south- ward and thence westward, perhaps passing into a small-leaved species. Maclura aurantiaca, the Osage Orange, belongs to the northwestern bor- ders of the Atlantic district. None in the western floras.
PLATANACE &@.—There is one Atlantic and one Californian Platanus ; but none intervening, except on the Mexican borders.
LEITNERIE2.—The anomalous Leitneria, of Florida, is of a single spe- cies, of wholly obscure affinity.
JUGLANDACE®.—Juglans cinerea and J. nigra or the Walnut trees of the Atlantic flora, J. California of the Pacific; Carya is of seven species, restricted to the Atlantic flora.
CUPULIFER &.—Are most fully represented in the Atlantic flora, are prominent in the Pacific flora, but are wanting in the whole interior region, excepting a Scrub Oak or two on the Rocky Mountains and their accessories. There are twenty-one Oaks, two Chestnuts, and a Beech in the Atlantic flora; nine Oaks and a Castanopsis in the Pacific flora; one Oak in the Rocky Mountain flora, or perhaps more than one; and two or three others in the district between it and Mexico.
CoRYLACE&.—An Ostrya and a Carpinus and two species of Corylus represent this group in the Atlantic flora. The two western floras want all but one of the latter, which traverses the continent.
BETULACE@.—Are represented in the Atlantic flora by seven Birches and three Alders. One of the smaller Birches and perhaps one of the Alders, extends over to the Pacific flora, along with another Rocky Mountain Birch, and two or three Alders are added.
MyRICACEa.—The amphigzan Myrica Gale is of the Atlantic flora; one very like it in the Pacific. Of the Bayberry Myrice, there are one or two on the Atlantic, and another on the Pacific coast. The Comp- tonia is peculiar to the Atlantic flora.
SALICINE &.—There are about fifteen Willows indigenous to the At- lantic States, nineteen in the Californian flora, very few of them iden- tical; the Rocky Mountains have a few of these and one or two more of alpine type. There are six Poplars in the Atlantic States; three or four in California and Oregon; one or two in the intermediate country, be- sides P. tremuloides, which, passing along the mountains, is common to all three floras.
The Gymnospermee may best be exibited under the particular groups.
GNETACEA.—Ephedra, the only extratropical genus, is absent from
4GB
50 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.V1.
the Atlantic flora, has three or four species in the Texano-Arizonian region, two of which enter the Great Basin, and one belongs to the southern part of California.
TAXINEZ are absent from the Rocky Mountain flora. The Atlantic flora has the depressed Taxus Canadensis at the north, and an upright arborescent and perhaps peculiar species in the northern part of Florida. There is a similar one in the woods of the Pacific side of the continent. The Atlantic flora possesses the original Torreya; California another ; the two remaining species are of Northeastern Asia.
CUPRESSINEa.—The amphigzean Juniperus communis traverses the continent at the north; and a prostrate form of J. Sabina probably does the same; also J. Virginiana, the eastern Red Cedar. But on a south- ern range the latter species hardly passes out of the Atlantic region. J. occidentalis and J. Californica are the characteristic species of the mountiuins bordering and traversing the southern part of the Great Basin and of California. Cupressus is wanting to the Atlantic and to the Rocky Mountain floras, but there are three species in the Pacific flora. Chamecyparis is of one species in the Atlantic flora, two in the Pacific, the remainder in Japan. Thwa is of two species, one of the Atlantic flora, the other of the Pacific and of Japan. JLibocedrus is represented by a peculiar species only in the Pacific flora.
TAXODINEX.—Of Taxodium distichum, in the Atlantic flora; Sequoia. gigantea and S. sempervirens, the Big Trees and Redwoods, in California.
ABIETINE &.—Are more numerous in North America than elsewhere. Like the preceding, they prefer the sides to the center of the continent, yet are not wanting to the mountains of the latter. Pinus is represented in the Atlantic flora by twelve species; in the Rocky Mountains and those of the Great Basin by six different species, not counting those of Arizona; in the Pacitie flora by eleven species, four of which are in the preceding flora. Larix has a single Atlantic and two Pacific species, one or both of which occur in the Northern Rocky Mountains. Picea, the Spruces, two in the Atlantic, two others in the Rocky Mountain, and two in the Pacific flora, one of the latter a Rocky Mountain species. Tsuga, one (Hemlock Spruce) in the Atlantic, and one almost the same in the Pacific flora, which has also the peculiar T. Pattoniana or Williamsonii. Pseudotsuga Douglasii, of the Pacific and the Rocky Mountain flora, most abundant in Oregon. Abies, the Firs or Balsam. Firs, two in the At- lantic, two in the Rocky Mountain, and four or five in the Pacific flora, one of them common ?
CYCADACE&.—Being represented only by a Zamia on the peninsular part of Florida, are beyond our limit.
The monocotyledonous orders must be more briefly dispatched.
PALME #.—Are represented on the Atlantic coast and north of the — Florida peninsula by four species in two genera. Three species in two genera are described in the Botany of California; but two of them are known only beyond the United States boundary; the other belongs properly to the Arizonian flora.
No.1] 'GRAY AND HOOKER ON THE ROCKY MJUNTAIN FLORA. Dl
ARACEA.—Absent from the whole interior region; represented by seven genera in the Atlantic flora, of which Peltandra and Orontiwm are peculiar, and Symplocarpus, except that it is reproduced in Japan; on the Pacific coast only a relative of the latter, Lysichiton, of which the same species occurs in Japan.
LEMNACEZ, TYPHACE2.—Both nearly the same on the two sides of ‘the continent.
NAIADACEa.—In similar case, except that the Pacific coast adds Lilea and Phyllospadix.
- ALISMACEZ:.—Not dissimilar, except that the Atlantic flora has sey- eral species of Sagittaria and the Pacific only one, but it has the Euro- pean type of Damasonium.
HYDROCHARIDACEH.—The Atlantic flora possesses Zimnobium and Vallisneria as well as Anacharis; the Pacific, only Anacharis; the intermediate region none.
BURMANNIACE.—Two Atlantic genera and species of South Amer- ican affinity ; none in the western floras.
ORCHIDACEH.—Are much fewer in the Pacific flora than in the Atlantic, and are wanting in the intermediate region, except on the mountains, and there in mostly amphigzean species. The Atlantic flora has the peculiar genera Tipularia and Arethusa (but the latter is in Japan), and some peculiar Habenaric ; the Pacific possesses two Euro- pean genera, Cephalanthera and LEpipactis, but the latter is also in Texas, and an Huropean species of it has recently been detected in the State of New York.
CANNACEZ.—Two genera and three species in the southern part of the Atlantic flora only.
AMARYLLIDACEH.—Are represented in the Atlantic flora by five genera, none of them peculiar, and several species. There are none in the two western floras except Agave, and those of Mexican type, and only along the southern border.
H#MODORACE#.—Three genera, all strictly peculiar to the Atlantic States.
BROMELIACE &.—Tillandsia only along the Atlantic coast; one spe- cies north to Virginia; others in Florida and its northern border.
IRIDACEH.—Two peculiar genera in the Atlantic flora or its borders, besides Lris and Sisyrinchiwm, which are more numerous in the Pacific flora; the former along the mountains between.
DIOSCOREACEH.—A single Dioscorea, in the Atlantic flora only.
SmiLACEzs.—A dozen species of Smilax in the Atlantic flora; one of them barely reaches the Rocky Mountains; a single and ferabed species in California.
ROXBURGHIACEA.— Oroomia, asingle species, in the Southern Atlantic States; a close congener in Japan; all other relatives Asiatic.
LiL1AcE.a.—Here taken in the extended sense, are largely represented {by twenty-four genera) in the Atlantic flora; are not very few in the
52 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.vI.
Rocky Mountain region, yet of few genera; and are remarkably devel- oped and diversified in the Pacific flora, which has thirty-three genera, several of them peculiar. Only eleven of the forty North American genera are European, but several of those otherwise peculiar are shared with Eastern Asia, especially the Melanthiee. The characteristic feat- ures of the Liliaceous vegetation of the two western floras are given by the endemic genera, Brodiwa and relatives, Leucocrinum, Chlorogalum, Calochortus, &e., by Yucca, which is also Atlantic, and by the great development of the genus Alliwm, exceeded only in Northern Asia.
JUNCACE4.—Are numerous and well distributed over the continent, but require no special remark.
PONTEDERIACE&.—Tropical aquatics, except the three genera of the Atlantic flora, one of which (Schollera) reappears in its single species. on the Pacific coast.
CoMMELYNACE&.—Also mainly tropical; are represented by two genera and several species in the Atlantic flora; one or two of these barely reach the Rocky Mountains southward; all are absent from the Pacific flora.
XYRIDACE Al.— Mayaca, a South American aquatic, and sixteen spe- cies of Yyris are characteristic of the Atlantic flora; are wanting to the others.
HRIOCAULONEA.—Chiefly Atlantic South American; are of three genera and several species in the Atlantic flora, but none at all western. The remarkable thing is that the most northern Hriocaulon has effected a lodgment on the coast of the British Islands.
CYPERACEZ.—The number of species and genera in the Atlantic flora is nearly double that of the Pacific, and the Rocky Mountain flora. has few.
GRAMINEZ, which would be well worth a particular analysis, are more equally AVtee, at least as to genera. Of these the western floras have many, chietly of Texano-Arizonian and Mexican types, which are un- known at the east. The Atlantic flora possesses a few peculiar genera, Zizania, Brachyelytrum, Monanthochloa, Hydrochloa, Ctenium, Oryzopsis, Graphephorum, Diarrhena (reproduced in Japan’), Gymnostichum, Trip- sacum. —
It is hardly worth while to extend this survey into the Cryptogamia, even to the Ferns.
“The subjoined tabular view of the Phznogamous orders presents to the eye some of the facts which the preceding pages have brought out. as regards respectively their presence or absence or their relative im- portance in the three floras which we have been comparing. The name in full capitals indicates that the order or group has its headquarters in the flora of that column. Small capitals indicate a full or a notable tepre- - sentation, at least comparatively. The name in ordinary Roman letters indicates a more or less considerable representation ; in italic type, a less or scanty representation ; the initial with a dash (as N in the
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 53
sixth line), indicates a feeble representation ; the blank means that the order is not indigenous to that flora. Thus, the second, third, and fourth orders are not represented, so far as we know, in the Rocky Mountain and the Pacific floras, 7. ¢., they do not extend westward beyond the Atlantic forest region. The next line declares that the order Berberidacee is, considering the size of the order (in this instance small), richly repre- sented in the Atlantic flora, sparingly in that of the Rocky Mountains (inclusive of the plains on the east and the desert basin on the west), more numerously in that of the Pacific district. Nympheacee are in the same case, having very full generic representation in the Atlantic flora but hardly any in that of the Rocky Mountains, and a little more on the Pacific side of the continent. Sarraceniacece take full capitals in the first column, not that the species or types are numerous, but because the few and remarkable Sarracenias represent the whole order, excepting two species; one of them is in California, and the Pacific column is en-
tered accordingly,
general way it tells the story.
Such a presentation is only approximate, but in a
Crassulacer. -DROSER ACE.
Crassulacee.
D
| | Pacific Flora.
Atlantic Flora. Rocky Mountain Flora. Ranunculacez. Ranunculacezx. | Ranunculacee. MAGNOLIACER. Anonacez. Menispermacez. BERBERIDACEE. Berberidacee. Berberidacesz. NYMPH ACER. Nympheacee. SARRACENTACEA. Sarraceniacee. Papaveracez. 12 PAPAVERACEE. ariacee. Fumariacec. Fumariacez. ‘Crucifere. Crucifere. Crucifere. Capparidacez, CLEOME. Capparidacez, CLEOMEZ. Capparidacer, Cleomess, Cistacezx. C : Violacex. _ Violacece. Violacez. Polygalacez. : K Saas & Krameriacee. K A Frankeniaces. Frankeniacex. Caryophyllacez. Caryophyllacez. Caryophyllacess ILLECEBRACE. Tlecebracez. Illecebracece. Portulacacee. PORTULACACER. PORTULACACEZ Elatinacezr. Elatinacez. Elatinaceer. HYPERICACER. Hypericacee. Ternstremiaceex. Malvacezr. Malvacez. Malvacez. Bombacez. Tiliacee. Linacee. Tinacee. Linacee. Zygophyllacec. -Geraniacee proper. Geraniacee. Geraniacee. Limnanthes. LIMNANTHEZ. Oxalidee. Ozalidee. Oxalidece. Balsaminex. Rutacex. R——. R CYRILLEE. Aquifoliacer. -Celastraceex. C ‘ Oelastracee. Rhamnacex. Rhamnacex. RHAMNACER. VITACER. 5 Vitacee. SAPINDACEZ. Sapindacee. Sapindacee. ANACARDIACEX. Anacardiacee. Anacardiacesr. PAPILIONACER. Papilionacez. PAPILIONACEZ, Cesalpinez. i Mimosee. Mimosee. ‘Chrysébalanec. yedalex. Amygdalee. Amygdalee. Rosacex propria. Rosacex. Rosacex. Pome. Pomee, Pomee. CALYCANTHACEZ. Calycanthacee. SAXIFRAGACEZ. Saxifragacex. | SAXIFRAGACER.
Crassulacex. D
54 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.Vz.
Atlantic Flora.
Hamamelides. Haloragez. _Melastomacex. Lythracez. Onagracez.
Turneracee. Passifloracex. Cucurbitacee. Oactacee. Ficoidee. Umbelliterz. Araliacez. Cornacez. Caprifoliacex. Rubiacezx. Valerianacez. Vernoniaces. Kupatoriaces. Asteroidex. Inuloidec. Helianthoidex. Galinsogec.
Helenioidee. Anthemidee. Senecionidee. _ Cynaroidee. Mutisiacee. Cichoracee. Lobeliacex. OCampanulacee. VACCINE. ERICINE. PYROLINEZ. MONOTROPES.
DIAPENSIACEA. Plumbaginaeece. Primulacez. Sapotacce. Ebenacee. Styracacez. Oleacez. Apocynacez. Asclepiadaces. Loganiacece. Gentianacez. Polemoniacez. Hydrophyllacee. Borraginacee. Convolvulacez. Solanacee. Scrophulariacex. Orobanchacex. Lentibulacez. Bignoniacez. Acanthacez. Verbenacez. Labiate. Plantaginacee.
Amarantacee. Phytolaccacec.
Polygonacez, proper.
Podostemacee. Aristolochiaceze. Saururee. Lauracee. Thymeleacec. Eleagnacee. Loranthacec. SANTALACEA. Huphorbiacee. EMPETRACE. Urticee. Ulmacee. Cannabiner. Moree. Platanacez. LEITNERIEA. JUGLANDACEZ. CUPULIFERZ.
Rocky Mountain Flora.
H—.
L ONAGRACER. LOASACEA.
Cucurbitacee. CACTACER. Ficoidee. UMBELLIFERZ.
Cornacee. Caprifoliacee. Rubiacee. Valerianacece.
Hupatoriacee. Asteroide. Inuloidec.
| Helianthoidex.
Madiee. HELENIOIDER. Anthemidezx. Senecionidex. Cynaroidee. Mutisiacee. Cichoraceez. Lobeliacee. Campanulacec. Vaecinee. Bricinee. Pyrolinee. Monotropec.
12 a Primulacezx.
O
Apocynacee.
Asclepiadacesx.
Gentianacex. POLEMONIACES.
HYDROPHYLLACEA.
Borraginacee. Convolvulacece. Solanacece. SCROPHULARIACES. OROBANCHACE. B——_.
A ‘: Verbenacee. Labiate. Plantaginacece. Nyctaginacez. Amarantacee.
POLYGONACEA. ERIOGONEZ.
Elzagnacez. Loranthacece. Santalacece. Buphorbiacee.
v——. U : Cannabinec.
Pacific Flora.
H——.
L——. ONAGRACEA. Loasacez.
Cucurbitacee. Cactaceze.
UMBELLIFERA. Araliacee. Cornacess. Caprifoliacec: Rubiacee. Valerianacesz.
Eupatoriacex. Asteroidec. TInuloidess. Helianthoidee. G
MADIEA. HELENIOIDE. Anthemides. Senecionidee. Cynaroidece. Cichoracee. LOBELIACE. Campanulacee. Vaccinee. Ericinez. Pyrolinee. MONOTROPEZ. Lennoacez.
Plumbaginacee. Primulacee.
Ss 4 Oleacee. Apocynacee. Asclepiadaceee.
Gentianacee. POLEMONIACEA,
| HYDROPHYLLACEA.
Borraginaceer. Convolvulacece. Solanacee. SCROPHULARIACEZ. Orobanchaceer.
A : Verbenacee. Labiate. Plantaginacee. Nyctaginaces.
| Amarantacec.
POLYGONACEE
| ERIOGONEZ.
Aristolochiacex. Saurureze. Lauracec.
| Thymeleacece. | Eleagnacec.
Loranthacee.
| Santalacece. | Huphorbiacec.
| Urticece. .
Platanacez.
Juglandacee. Cupulifers.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA, 55
Atlantic Flora. Rocky Mountain Flora. Pacific Flora, Corylacez. Cc A Cc : BETULACER. Betulacece. Betulacesx. Myricaces. Myricacee.
icinex. Salicinee. Salicines. Gnetaces. Gnetacee. Taxinex. : Taxiner. Cupressines. Oupressinee. CUPRESSINEZ. Taxodinesx. Taxodines. ' Abietines. Abietinece. ABIETINER. Palmee. Palmee. Araces. Aracee. Lemnacez. L——. Lemnacen. pyRnecer. Typhacee. Typhacesx. ismaces. A: - Alismaces. Hydrocharidaceax. . Burmanniacex. Oannacec. Orchidaces. Orchidacee. Orchidaces. Amaryllidacez. Hemodoracen. Bromeliacec. Tridacex. Tridacee. Iridaces. Dioscoreacece. Roxburghiacesx. Smilacez. S - Smilacece. Liliacee. Liliacex. LILiAckz&. Juncaces. Juncacez. Juncaces. Pontederiaces. Xyridacex. Eriocaulones. CYPERACER. Oyperacee. Cyperaces. Graminez. Gramines. Graminez.
The groups in this tabulation, it will be observed, have not all the rank of orders. Such as they are, the—
2 SISO TNO ae AAs Oe eee Meee i Merc Rey rk ea 156 Rocky Mountain flora (in most extensive semse)....---..--------- 112 Te SoMTEG TOI) obi elorge eo ae se Sie aetna eect ear a se 5 Sa, eee
But of the groups very slightly represented there is only one in the first, while there are twenty-four in the Rocky Mountain flora and fifteen in the Pacific. If these be omitted the greater diversification of the At- lantic flora will be the more apparent—
Atlantic orders or groups..........-- Beeb teen At aah EEE ease IS 155 Rocky Mountain............ Eheveh rate a. RT soe NOSE MP eT aS ar 88 LEE SVE vere eps yb anes ae IN le Ni el aa ea de NS oy) ASE,
As to the numerical extent, respectively, of these three great divisions of the United States flora, exactness would be attainable only through much labor; and an approximation is nearly as valuable as would be a close count from present and still changing data. Mann’s Catalogue of the Phzenogamous Plants of the United States east of the Mississippi, may be taken for the Atlantic flora, excluding for our purpose the intro- duced species and those of the Florida peninsula. The official Botany of California, mainly by S. Watson, now just completed, includes or men- tions the greater part of the Pacific species and genera, but includes many which, though indigenous to that State or near its borders, really pertain only to the flora of the interior basin. Mr. Watson’s careful elaboration of the botany of this basin and its borders, presented in his volume (V.) of Clarence King’s Explorations and Surveys on the For- - tieth Parallel, sums up and analyzes the vegetation of this distriet; but
56 BULLETIN UNITED STATES GEOLOGICAL SURVEY. (Vol. VI.
for the proper Rocky Mountains and the eastern plains no such summary is at hand, although Porter and Coulter’s Flora of Colorado has brought together some of the materials.
We may estimate that the Atlantic flora north of the thirtieth parallel (and wholly excluding Texas) consists of 850 Phenogamous genera and 3,400 species; that the Pacific flora as now known does not exceed 620 genera and 3,000 species. Mr. Watson ten years ago had knowledge of 1,235 species in 439 genera (and 84 orders) in the Great Basin and the adjacent Wahsatch and Uinta Mountains. If the ratio of genera and species to orders is the same as in the Atlantic States, the whole Rocky Mountain flora, from its eastern plains to the Sierra, and within the designated parallels of latitude, would contain about 480 genera and 1,930 species; and this is probably not far from the mark.
The botanist will see at a glance the principal contrasts between the Atlantic and Pacific floras. The Atlantic is the region of round-headed and deciduous-leaved trees; the Pacific of spire-shaped, evergreen, Coniferous trees; and the Rocky Mountain forest is of the same type as that of the Pacific, only on a diminished scale, and with the more strik- ing forms left out.
The Atlantic flora has almost three times as many genera and four times as many species of non-Coniferous trees as the Pacific, but it has rather fewer genera and almost one-half fewer species of Coniferous trees than the Pacific.
The forest of the Atlantic States is, with one exception (that of North- eastern Asia), much the most diversified, 7. ¢., the richest in genera and orders, as well as species, of any other temperate region. That of the Pacific is one of the least diversified, except for its Conifere. Both together are remarkable for the persistence in them of certain peculiar archeological types of the latter, namely, Taxodiwm and Torreya on the Atlantic side, Torreya, Libocedrus, and, above all, Sequoia, on the Pacific.
The Atlantic forest is of no inferior grandeur; few parts of the north- ern hemisphere equal it in the stateliness of its trees, but the grandeur of the Pacific forest growth as to Coniferous trees is wholly unequaled.
These points have been brought out in a discourse by the present writer (entitled Forest Geography and Archeology), which was pub- lished in the American Journal of Science and Arts, ser. 3, xvi, 1878, and which, having been prepared in view of this report, it is proposed to append ane more important portions of it.
There are certain orders or groups in which the diversification of types and the number of forms in the Pacific flora much surpasses that of the Atlantic, and it is to these that the salient features of the former are mainly to be attributed; and in referring to these, the western interior flora, sharing in these features, may be taken with the Pacific flora proper.
The largest of all the Phenogamous orders, the Composite, used to be reckoned as constituting a tenth part of the Phenogamous vegetation
No.1] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 57
of the world and an eighth part of that of North America. It forms fully an eighth part of the Atlantic flora. It appears to form between a sixth and aseventh part of the species in the district west of the Rocky Mountains, and a still larger proportion of the genera. Here are found most of the Helenioidew and almost all the Madiew, and of the other tribes there is no lack, except of Vernoniacew.
The Scrophulariacec are far more conspicuous and preponderant on the western side of the continent, not so much, if atall, in genera, but vastly in the number of species. This is mainly owing to the wonderful devel- opment of certain genera (Pentstemon, Mimulus, Castilleia, Orthocarpus), - as has been already stated.
The Polemoniacee form an even more marked feature, the western flora having more genera, indeed five times as many forms and five times as many species as the eastern.
‘The Hydrophyllacew are in nearly a similar case; the Borraginacee approach to it, and so do the Chenopodiacee.
The Hriogonee, however, claim the first rank; considering the num- ber of the species and the distribution of the group, no other group of ordinal or subordinal rank is so completely characteristic of Western North American botany as this.
Finally, as to the Liliacew (in the extended sense), although the At- lantie flora is rich in them, yet the Pacific region considerably surpasses it in the number of genera, and largely surpasses it in the number of Species and in the conspicuousness of the flowers.
JOR NORTH AMERICAN TYPES IN SOUTH AMERICA.
The botany of the southern part of the eastern great plain of the interior arid district, and of Southern California, merges in that of the Texano-Arizonian belt, and.this into that of the Mexican plateau. It is probable that from these plateaux our western regions received the greater part of their present forms and types.
We may expect soon to know more than we now do of the botany of the cooler parts of Mexico, and to have this knowledge in a conveni- ently available form.
It appears, however, that the Texano-Arizonian species or their repre- sentatives do not prevail far down into Mexico, and that the arctic- alpine species and other northern types of the higher mountains are soon replaced southward by andine forms.
There are clear if not very numerous indications that there has at some former time been greater opportunity than now for the extension of North American species and types into the southern hemisphere. And it appears that this has taken place mainly along the western side of the American continent, on which the mountains abut on the coast— that is. as respects American plants which have found their way to
58 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VI.
extra-tropical South America. On the Atlantic side there appears to have been only a slight commingling of warm-temperate United States plants with the flora of the nearer tropical districts. Thus, the island of Cuba has Pinus Elliottii (Cubensis), [llicitum parviflorum, some species . of Asimina, all the Nymphceacece of the Atlantic flora, Ascyrwm ampleat- caule, &e., our Ampelopsis and Vitis bipinnata, Ilex Dahoon, a Rhexia, Oldenlandia glomerata, Houstonia patens, Pterocaulon, Andromeda nitida, Cyrilla, Sabbatia gracilis, Mitreola petiolata, Lachnanties tinctoria, Mayaca, &e. These, the Ampelopsis excepted, are peculiar to the Atlantic coast. Cuba, moreover, has a species of Kalmia !
But more speculative interest arises from the consideration of the North American types, and in many cases the actual species, which re- appear beyond the tropic in South America, on the western and not rarely on the eastern ‘side of that continent. There are a number of plants indigenous to Chili, the presence of which in California—where they are seemingly no less indigenous—may be accounted for by the immigration of men and cattle. This may have been the case with Senebiera, Pentacena, Acena trifida, Plectritis (Betkea) samolifolia, Bow- lesia lobata, Amblyopappus pusillus, Pectocarya, Lastarriea, and the like. For Erodium cicutarium, Medicago denticulata, Melilotus parviflora, Oli- gomeris subulata, and Avena fatua, which are now equally at home in. California, probably arrived by that route rather than direct from Hu- rope. But we cannot in this way explain the presence in the two tem- perate zones of plants such as the following, which we assume to be North American species or types dispersed into South America. Some few of them might with equal likelihood be viewed as Chilian types with abnormal northern dispersion. We enumerate only such as come to view without particular search, and exclusive of those which may have been dispersed under man’s unconscious agency. Identical species in italics :
Anemone decapetala.
Anemone multifida.
Myosurus aristatus.
Sisymbrium canescens.
Vesicaria, said to be arctica.
Malvastrum of North American type.
Spheralcea of North American type.
Modiola multifida (Atlantic).
Sida (Pseudo-Malvastrum) sulphu- rea.
Hlatine Americana.
Larrea.
Rhus § Lithreea.
Lupinus microcarpus.
Trifolium Macret.
Trifolium microdon.
Hosackia subpinnata.
Lathyrus maritumus.
Hoffmanseggia.
Prosopis (Algarobia) julifiora.
Prosopis (Strombocarpa) sp. aff.
Fragaria Chilensis.
Lepuropetaton spathulatum (Atlantic and Chilian).
Gayophytum sp.
Cinothera sp. aff.
CGinothera dentata.
Ginothera cheiranthifolia.
Boisduvalia sp.
Godetia sp.
Mentzelia sp. aff.
No. 1.]
Crantzia lineata.
Hydrocotyle ranunculoides, Sse.
Osmorrhiza.
Galium § Relbunium.
Galium § Trichogalium.
Mikania scandens ?
Gutierrezia.
Grindelia.
Aplopappus.
Nardophyllum (aff. Bigelovia).
Micropus.
Adenocaulon.
Polymnia.
Thelesperma scabiosoides!
Madia sativa.
Jaumea linearifolia.
Lasthenia obtusifolia.
Bahia.
Sehkuhria.
Blennosperma Chilense.
Actinella sp.
Gaillardia (Cercostylis) (Bonaria).
Soliva (North American species im- migrated ?).
Centaurea (Plectocephalus) Chilen- SiS.
Microseris pygmea.
Downingia pusilla.
Specularia biflora.
Menodora sp.
Primula farinosa.
Microcala quadrangularis.
GRAY AND HOOKER ON THE ROCKY MOUNTAIN
59
FLORA.
Erythreea Chilensis.
Collomia gracilis, &e.
Gilia pusilla.
Gilia (Navarretia) involucrata.
Gilia laciniata.
Phacelia circinata.
Phacelia (Microgenetes) Cumingii.
Coldenia § Tiquilia.
Hritrichium fuloum, &e.
Amsinckia angustifolia.
Solanum eleagnifolium.
Physalis viscosa.
Mimulus luteus.
Orthocarpus australis.
(Verbena § Glandularia, &c.)
Plantago Patagonica.
Plantago hirtella.
Plantago maritima (Hu. &c.).
Oxybaphus sp.
Allionia incarnata.
Spirostachys sp.
Oxytheca dendroidea.
Chorizanthe sp.
Lastarreia Chilensis (mentioned above).
Podostemon.
Lileea subulata.
Scirpus riparius.
Scirpus tatora.
Hemicarpha subsquarrosa.
Gramine, several.
Ilere are near upon 90 species or genera, and almost half of them are
identical with a few proximately related species.
the Chilian side of the continent. eastern side.
Most of them affect
One or two are known only on the The most remarkable of these are the Gaillardia and the
Thelesperma, of Buenos Ayres; the former closely related to an equally anomalous Texan species; the latter almost identical with a Texano-Ne- braskan species. One of the Strombocarpa species of Prosopis, of the southern end of Texas, is hardly and perhaps not specifically distinguish- able from one of Buenos Ayres. Of the 40 or more identical species, only 17 belong to the Atlantic flora; apparently only two of these are peculiar to it as respects North America, namely, the little Lepuwropetalon of the Atlantic coast, not again met with this side of Chili, and the in- significant Modiola multifida. Quite possibly the latter was introduced into North America as a ballast weed.
60 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VI.
The natural and obvious line of communication between the botany of the northern and southern temperate zones has been along the central part of North America and Mexico, and along the western part of South America. When our cool temperate flora flourished only along or near the southern borders of the United States, the warm-temperate (to which most of the above-enumerated forms belong) were still further south. When the climate became again warmer, a portion of these plants were as well placed for southward as for northward retreat.
ID NOTES ON THE SOURCES OF THE NORTH AMERICAN FLORA.
Before yielding the pen to his associate, who will develop the rela- tions of the whole North American flora to those of other parts of the northern hemisphere, the present writer may sum up, without develop- ing them, one or two of the probable or plausible inferences or theo- retical deductions which the present state of our knowledge, gathered from a great variety of data, appear to enable us to draw. They are conclusions the acceptance of which affords at least a clue to the expla- nation of the condition, constitution, and seeming anomalies of the actual geographical distribution of the genera and species of our part of the world. The non-professional reader may best apprehend the ground of these deductions by a perusal of the discourse already referred to, which is appended to this report.
The present vegetation of the world is a continuation with successive modification of that of preceding geological times, and the plants indige- nous to any country are completely adapted to its climate, and there- fore are capable of enduring its extremes.
Accordingly the explanation of the present assignment of species and genera is to be sought partly in the geological past, partly in the actual climate. Questions of the latter kind are comparatively simple. There is no difficulty in understanding why our Atlantic region was naturally covered with forest, why the great plains toward the Rocky Mountains: are woodless, and why plains with a saline soil are abandoned to a vege- tation resembling that of sea-coasts. There is no insuperable difficulty in comprehending how high mountains may nourish forests, even when favored with little absolute rainfall. The difficulty is in ascertaining how a particular species of tree or other plant came to be a constituent of a certain flora, at stations widely separated from its nearest relatives, or even from other members of the same species. This is not a difficulty, but only a sterile wonder, to those who suppose that facts of this order have no scientific explanation, or none which they can hope to reach. It is one only to those who assume that all the members of a species, and even all the species of a natural genus, were derived at some time or other from a common stock; but this is the assumption now generally made in natural history. A reference to the existing state of things will
Nol.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 6h
seldom answer questions of this kind; but a reference to the past may sometimes do so.
Although the vegetable paleontologist goes farther back, the botanist of our era, in the discussion of his problems, may take the Tertiary period for his point of departure. At least, the key to the distribution of the flora of the temperate regions of the northern hemisphere— with which we are concerned—is afforded by the later Tertiary botany.
Our knowledge—fragmentary, yet real—of the flora around us begins. with a period when it or its direct ancestors occupied the zone between the arctic circle and the pole, and doubtless several lower degrees of latitude. There it must have flourished until the coming on of that change of climate which culminated in the glacial period. It must at that time have encircled that portion of the earth much as the arctic flora now does. During the period of maximum refrigeration, its north- ern limits, abutting upon an arctic flora then in low latitude, must have been so far south in the Atlantic States that the vegetation of the northern shore of the Gulf of Mexico probably resembled that of the southern shore of the Gulf of Saint Lawrence now. Of this northern limit there cannot be much doubt; yet we could not hazard an opinion as to where the warm-temperate vegetation of that day merged into the subtropical, as it now does in Southern Texas.
The change between that period and the present, in the opposite di- rection, has been an amelioration of climate which has carried the are- tic flora back to the arctic circle, with which we now associate it, except- ing the portions which, in the retreat, have ascended the mountains and persisted there, forming the navi. alpine vegetation. This, as we have seen, is very scanty in the Atlantic district, where it has abided only on the most northern mountains; while the more elevated ranges of the western part of the continent have afforded ampler refuge.
A similar advance and. ensuing retrogression, consequent upon the coming and going out of the Glacial epoch, must have taken, place in other parts of the northern hemisphere. Under these great and, pro- tracted movements, of transference, we suppose that a common, flora,
‘which was comparatively homogeneous round the new arctic zone, has. been differentiated into the several existing north-temperate floras, and that their common features, and the occasional very unexpected identi- ties or similarities (such as those between Japanese and North Ameri- can botany) are thus explained. Their respective peculiarities are thought to have resulted from the different vicissitudes and the different climatic conditions to which the primeval stock has been, exposed in Asia, Europe, and America, and upon the opposite sides and great in- teriors of continents, the climates of which—greatly different now—haye probably been so from very early times. The plants which were most adapted or adaptable to the one could not be expected to survive in another, or in any other than one of similar or analogous climate. But this is not the place for considering the application of these principles
62 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol.VL
to the botany of the northern hemisphere generally. When they come to be applied to the theoretical elucidation of the great difference be- tween the Atlantic and the Pacific floras it will need to be noted that the two sides of the continent, at the time when they received the pro- genitors of the present vegetation, were more completely separated than now; that they seem to have been, as it were, two long peninsulas stretching southward from a mainland at the north, the great plains between our eastern district and the Rocky Mountains being then under water.
It may be inferred that the Atlantic side of the continent was more open than the western to the reception of the ancestral flora from the north, and so received it in larger measure and variety, or that it has been since that time more free from disturbance and catastrophe. Proba- bly the two causes may have conspired in the production of the result. ‘There is, moreover, reason to suspect that the recession of the glaciation was earlier on the Atlantic side of the continent than in the more ele- vated central and Pacific regions; and that, from all these causes, its preglacial flora was more completely restored to it than to that of the Pacific side.
And, finally, we infer that the Pacific region, while preserving through all vicissitudes a moderate number of boreal types, and receiving a few Eastern Asiatic ones probably at a later date, has been mainly replen- ished from the Mexican plateau, and at a comparatively late period. A large part of the botany of California, still more of Nevada, Utah, and Western Texas, and, yet more, that of Arizona and New Mexico, may be regarded as a northward extension of the botany of the Mexican plateau.
This may, at least, be said: that two types have left their impress upon the North American flora, and that its peculiarities are divided between these two elements. One we may call the boreal-criental ele- ment ; this prevails at the north, and is especially well represented in the Atlantic flora and in that of Japan and Manchuria; the other is the Mexican-plateau element, and this gives its peculiar character to the flora of the whole southwestern part of North America, that of the higher . mountains excepted.
[From the American Journal of Science and Arts, Vol. XVI, 1878.] FOREST GEOGRAPHY AND ARCHAOLOGY.
By ASA GRAY.
[A lecture delivered before the Harvard University Natural History Society, April 18, 1878.}
* * * Tt is the forests of the northern temperate zone which we are to traverse. After taking some note of them in their present condition and relations, we may in- quire into their pedigree; and, from a consideration of what and where the compo- nent trees have been in days of old, derive some probable explanation of peculiarities which otherwise seem inexplicable.
In speaking of our forests in their present condition, I mean not exactly as they are to-day, but as they were before civilized man had materially interfered with them.
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 63 '
In the district we inhabit such interference is so recent that we have little difficulty in conceiving the conditions which here prevailed, a few generations ago, when the “forest primeval”—described in the first lines of a familiar poem—covered essentially the whole country, from the Gulf of Saint Lawrence and Canada to Florida and Texas, from the Atlantic to beyond the Mississippi. This, our Atlantic forest, is one of the largest and almost the richest of the temperate forests of the world. That is, it com- prises a*greater diversity of species than any other, except one.
_ In crossing the country from the Atlantic westward, we leave this forest behind us when we pass the western borders of those organized States which lie along the right bank of the Mississippi. We exchange it for prairies and open plains, wooded only along the water-courses—plains which grow more and more bare and less green as we proceed westward, with only some scattering Cottonwoods (i. e. Poplars) on the imme- diate banks of the traversing rivers, which are themselves far between.
In the Rocky Mountains we come again to forest, but only in narrow lines or patches; and if you travel by the Pacific Railroad you hardly come to any; the eastern and the interior desert plains meet along the comparatively low level of the divide which here is so opportune for the railway; but both north and south of this line the mountains themselves are fairly wooded. Beyond, through all the wide interior basin, and also north and south of it, the numerous mountain chains seem to be as bare as the alka- line plains they traverse, mostly north and south, and the plains bear nothing taller than Sage-brush. But those who reach and climb these mountains find that their ra- vines and higher recesses nourish no small amount of timber, though the trees them- selves are mostly small and always low.
When the western rim of this great basin is reached there is an abrupt change of scene. This rim is formed of the Sierra Nevada. Even its eastern slopes are forest- clad in great measure; while the western bear in some respects the noblest and most remarkable forest of the world—remarkable even for the number of species of ever- green trees occupying a comparatively narrow area, but especially for their wonder- ful development in size and altitude. Whatever may be claimed for individual Eu- calyptus trees in certain sheltered ravines of. the southern part of Australia, it is probable that there is no forest to be compared for grandeur with that which stretches, essentially unbroken, though often narrowed and nowhere very wide, from the south- ern part of the Signe Nevada in latitude 36° to Puget Sound, beyond latitude 49°, and not a little farther.
Descending into the long valley of California, the forest changes, dwindles, and mainly disappears. In the Pacific coast ranges it resumes its sway, with altered feat- ures, some of them not less magnificent and of greater beauty. The Redwoods of the coast, for instance, are little less gigantic than the Big-trees of the Sierra Nevada, and far handsomer, and a thousand times more numerous. And several species which are merely or mainly shrubs in the drier Sierra become lordly trees in the moister air of the northerly coast ranges. Through most of California these two Pacific forests are separate; in the northern part of that State they join and form one rich woodland belt, skirting the Pacific, backed by the Cascade Mountains, and extending through British Columbia into our Alaskan Territory.
So we have two forest regions in North America—an Atlantic and a Pacific. They may take these names, for they are dependent upon the oceans which they respectively border. Also we have an intermediate isolated region or isolated lines of forest, flanked on both sides by bare and arid plains—plains which on the eastern side may partly be called prairies—on the western, deserts.
This mid-region mountain forest is intersected by a transverse belt of arid and alka- line plateau, or eastward of grassy plain—a hundred miles wide from north to south— through which passes the Union Pacific Railroad. This divides the Rocky Mountain forest into a southern and a northern portion. The southern is completely isolated. The northern, in a cooler and less arid region, is larger, broader, more diffused. Trend- ing westward, on and beyond the northern boundary of the United States, it approaches,
64 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VE..
and here and there unites with, the Pacific forest. Eastward, in northern British territory, it makes a narrow junction with northwestward prolongations of the broad Atlantic forest.
So much tor these forests as a whole, their position, their limits, Before we glance at their distinguishing features and component trees, I should here answer the ques- tion, why they occupy the positions they do; why so curtailed and separated at the south, so much more diffused at the north, but still so strongly divided into eastern and western? Yet I must not consume time with the rudiments of physical geography and meteorology. It goes without saying that trees arenourished by moisture. They starve with dryness and they starve with cold. A tree is a sensitive thing. With its great spread of foliage, its vast amount of surface which it cannot diminish or change, except by losing that whereby it lives, it is completely and helplessly exposed to every atmospheric change; or at least its resources for adaptation are very limited, and it cannot flee forshelter. But trees are social, and their gregarious habits give a certain mutual support. A tree by itself is doomed, where a forest, once established, is com- paratively secure.
Trees vary as widely as do other plants in their constitution; but none can with- stand a certain amount of cold and other exposure, nor make head against a certain shortness of summer. Our high northern regions are therefore treeless, and so are the summits of high mountains in lower latitudes. As we ascend them we walk at first under Spruces and Fir-trees or Birches; at 6,000 feet on the White Mountains of New Hampshire, at 11,000 or 12,000 feet on the Colorado Rocky Mountains, we walk through or upon them; sometimes upon dwarfed and depressed individuals of the same species that made the canopy below. These depressed trees retain their hold on life only in virtue of being covered all winter by snow. At still higher altitude the species are wholly different, and for the most part these humble alpine plants of our temperate zone—which we cannot call trees, because they are only a foot or two or a span or two. high—are the same as those of the arctic zone, of Northern Labrador, and of Green- land. The arctic and the alpine regions are equally unwooded from cold.
As the opposite extreme, under opposite conditions, look to equatorial America, on the Atlantic side, for the widest and most luxuriant forest-tract in the world, where winter is unknown, and a shower of rain falls almost every afternoon. The size of the Amazon and Orinoco—brimming throughout the year—testifies to the abundance of Tain and its equable distribution.
The other side of the Andes, mostly farther south, shows the absolute contrast, in the want of rain and absence of forest; happily it isa narrow tract. The same is true- of great tracts either side of the equatorial regions, the only district where great des- erts reach the ocean. .
It is also true of great, continental interiors out of the equatorial belt, except where cloud-compelling mountain-chains coerce a certain deposition of moisture from air which, could give none to the heated plains below. So the broad interior of our coun-- try is forestless from dryness in our latitude, as the high northern zone is forestless. from cold.
Regions with distributed rain are naturally forest-clad. Regions with scanty rain, and at one season, are forestless or sparsely wooded, except they have some favoring compensations. Rainless regions are desert.
The Atlantic United States in the zone of variable weather and distributed rains, and with the Gulf of Mexico as a caldron for brewing rain, and no continental expanse between that great caldron and the Pacific, crossed by a prevalent southwest wind in summer, is greatly favored for summer as well as winter rain.
And so this forest region of ours, with annual rainfall of 50 inches on the Lower Mississippi, 52 inches in all the country east of it bordering the Gulf of Mexico, 45 to- 41 in all the proper Atlantic district from East Florida to Maine, and the whole region drained by the Ohio—diminished only to 34 inches on the whole Upper Mississippi and Great Lake region—with this amount of rain, fairly distributed over the year, and the - greater part not in the winter, our forest is well accounted for.
No.1.] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 65
The narrow district occupied by the Pacific forest has a much more unequal rainfall, more unequal in its different parts, most unequal in the different seasons of the year, , very different in the same place in different years.
From the Gulf of Mexico to the Gulf of St. Lawrence the amount of rain decreases moderately and rather regularly from south to north; but, as less is needed in a cold climate, there is enough to nourish forest throughout. On the Pacific coast, from the Gulf of California to Puget Sound, the southerly third has almost no rain at all; the middle portion less than our Atlantic least; the northern third has about our Atlantic average.
Then, New England has about the same amount of rainfallin winter and in summer ; Florida and Alabama about one-half more in the three summer than in the three winter months—a fairly equable distribution. But on the Pacific coast there is no summer rain at ail, except in the northern portion, and there little. And the winter rain, of
forty-four inches on the northern border, diminishes to less than one-half before reach-
ing the Bay of San Francisco; dwindles to twelve, ten, and eight inches on the southern coast, and to four inches before we reach the United States boundary below San Diego.
Taking the whole year together, and confining ourselves to the coast, the average rainfall for the year, from Puget Sound to the border of California, is from eighty inches at the north to seventy at the south, %. ¢, seventy on the northern edge of California; thence it diminishes rapidly to thirty-six, twenty (about San Francisco), twelve, and at San Diego to eight inches.
The two rainiest regions of the United States are the Pacific coast north of latitude forty-five, and the northeastern coast and borders of the Gulf of Mexico. But when one is rainy the other is comparatively rainless. For while this Pacific rainy region has only from twelve to two inches of its rain in the summer months, Florida, out of its forty to sixty, has twenty to twenty-six in summer, and only six to ten of it in the winter months.
Again, the diminution of rainfall as we proceed inland from the Atlantic and Gulf shores, is gradual; the expanse that is or was forest-clad is very broad, and we wonder only that it did not extend farther west than it does.
On the other side of the continent, at the north, the district so favored with winter rain is but a narrow strip, between the ocean and the Cascade mountains. East of the latter the amount abruptly declines—for the year from eighty inches to sixteen; for the winter months, from forty-four and forty to eight and four inches; for the summer months, from twelve and four to two and one.
So we can understand why the Cascade Mountains abruptly separate dense and tall forest on the west from treelessness on the east. We may conjecture, also, why this North-Pacific forest is so magnificent in its development.
Equally, in the rapid decrease of rainfall southward, in its corresponding restric- tion to one season, in the continuation of the Cascade mountains as the Sierra Nevada, cutting off access of rain to the interior, in the unbroken stretch of coast ranges near the sea, and the consequent small and precarious raintall in the great interior valley of California, we see reasons why the Californian forest is mainly attenuated south- ward into two lines—into two files of a narrow but lordly procession, advancing southward along the coast ranges, and along the western flank of the Sierra Nevada, leaving the long valley between comparatively bare of trees.
By the limited and precarious rainfall of California, we may account for the limi- tations of its forest. But how shall we account for the fact that this district of comparatively little rain produces the largest trees in the world? Not only produces, alone of all the world, those two peculiar Big-trees which excite our special wonder their extraordinary growth might be some idiosyneracy of a race—but also produces Pines and Fir-trees, whose brethren we know, and whose capabilities we can estimate upon a scale only less gigantic. Evidently there is something here wonderfully favor-
5GB
66 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VI.
able to the development of trees, especially of coniferous trees; and it is not easy to de ermine what it can be.
Nor, indeed, does the rainfall of the coast of Oregon, great as it is, fully account for the extraordinary development of its forest; for the rain is nearly all in the winter, very little in the summer. Yet here is more timber to the acre than in any other part of North America, or perhaps in any other part of the world. The trees . are never so enormous in girth as some of the Californian, but are of equal height— at least on the average—three hundred feet being common, and they stand almost within arms’ length of each other.
The explanation of all this may mainly be found in the great climatic differences between the Pacific and the Atlantic sides of the continent; and the explanation of these differences is found in the difference in the winds and the great ocean currents.
The winds are from the ocean to the land all the year round, from northwesterly in summer, southwesterly in winter. And the great Pacific Gulf Stream sweeps toward and along the coast, instead of bearing away from it, as on our Atlantic side.
The winters are mild and short, and are to a great extent a season of growth, instead of suspension of growth as with us. So there is a far longer season available to tree-vegetation than with us, during all of which trees may either grow or accu- mulate the materials for growth. On our side of the continent and in this latitude, trees use the whole autumn in getting ready for a six-months winter, which is com- pletely lost time.
Finally, as concerns the west coast, the lack of summer rain is made up by the moisture-laden ocean winds, which regularly every summer afternoon wrap the coast ranges of mountains, which these forests affect, with mist and fog. The Redwood, one of the two California Big-trees—the handsomest and far the most abundant and useful—is restricted to these coast-ranges, bathed with soft showers fresh from the ocean all winter, and with fogs and moist ocean air all summer. It is nowhere found beyond the reach of these fogs. South of Monterey, where this summer condensation lessens, and winter rains become precarious, the Redwoods disappear, and the gen- eral forest becomes restricted to favorable stations on mountain sides and summits. * * * The whole coast is bordered by a line of mountains, which condense the moisture of the sea-breezes upon their cool slopes and, summits. These winds, con- tinuing eastward, descend dry into the valleys, and, warming as they descend, take up moisture instead of dropping any. These valleys, when broad, are sparsely wooded or woodless, except at the north, where summer rain is not very rare.
Beyond stretches the Sierra Nevada, all rainless in summer, except local hail-storms and snowfalls on its higher crests and peaks. Yet its flanks are forest-clad; and, be- tween the levels of 3,000 and 9,000 feet, they bear an ample growth of the largest Co- niferous trees known. In favored spots of this forest—and only there—are found those groves of the giant Sequoia, near kin of the Redwood of the coast-ranges, whose trunks are from fifty to ninety feet in circumference, and height from two hundred to three hundred and twenty-five feet. Andin reaching these wondrous trees you ride through miles of Sugar Pines, Yellow Pines, Spruces, and Firs, of such magnificencein girth and height, that the Big-trees, when reached—astonishing as they are—seem not out of - keeping with their surroundings.
I cannot pretend to account for the extreme magnificence of this Sierra Forest. Its rainfall is in winter, and of unknown but large amount. Doubtless most of it is in snow, of which fifty or sixty feet falls in some winters ; and—different from the coast and in Oregon, where it falls as rain, and at a temperature which does not suspend vegetable action—here the winter must be complete cessation. But with such great snowfall the supply of moisture to the soil should be abundant and lasting.
Then the Sierra—much loftier than the coast-ranges—rising from 7,000 or 8,000 to 11,000 and 14,000 feet, is refreshed in summer by the winds from the Pacific, from which it takes the last drops of available moisture; and mountains of such altitude, to which moisture from whatever source or direction must necessarily be attracted,
Wo.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 67
are always expected to support forests, at least when not cut off from sea winds by interposed chains of equal altitude. Trees such mountains will have. The only and the real wonder is that the Sierra Nevada should rear such immense trees!
Moreover, we shall see that this forest is rich and superb only in one line; that, beyond one favorite tribe, it is meagre enough. Such for situation, and extent, and surrounding conditions, are the two forests—the Atlantic and Pacific—which are to be compared.
In order to come to this comparison I must refrain from all account of the interven- ing forest of the Rocky Mountains, only saying, that it is comparatively poor in the size of its trees and the number of species; that few of its species are peculiar, and those mostly in the southern part, and of the Mexican plateau type; that they are common to the mountain-chains which lie between, stretched north and south en eche- ion, all through that arid or desert region of Utah and Nevada, of which the larger part belongs to the Great Basin between the Rocky Mountains and the Sierra Nevada; that most of the Rocky Mountain trees are identical in species with those of the Pacific forest, except far north, where a few of our eastern ones are intermingled. I may add that the Rocky Mountains proper get from twelve to twenty inches of rain in the year, mostly in winter snow, some in summer showers.
But the interior mountains get little, and the plains or valleys between them less; the Sierra arresting nearly all the moisture coming from the Pacific, the Rocky Moun- tains all coming from the Atiantic side.
Forests being my subject, I must not tarry on the woodless plain—on an average 500 miles wide—which lies between what forest there is in the Rocky Mountains and ‘the western border of oureastern wooded region. Why this great sloping plain should be woodless—except where some Cottonwoods and their like mark the course of the tray~ ersing riyers—is, on the whole evident enough. Great interior plains in temperate latitudes are always wvodless, even when not very arid. This of ours is not arid to the degree that the corresponding regions west of the Rocky Mountains are. The moisture from the Pacific which those would otherwise share, is, as we have seen, arrested on or near the western border, by the coast-ranges and again by the Sierra Nevada; and so the interior (except for the mountains) is all but desert.
On the eastern side of the continent the moisture supplied by the Atlantic and the Gulf of Mexico meets no such obstruction. So the diminution of rainfallis gradual instead of abrupt. But this moisture is spread over a vast surface, and it is naturally be- stowed, first and most on the seaboard district, and least on the remote interior. From the Lower Mississippi eastward and northward, including the Ohio River basin, and so to the coast, and up to Nova Scotia, there is an average of forty-seven inches of rain in the year. This diminishes rather steadily westward, especially northwest- ward, and the western border of the ultra-Mississippian plains gets less than twenty inches.
-Indeed, from the great prevalence of westerly and southerly winds, what precipita- tion of moisture there is on our western plains is not from Atlantic sources, nor much from the Gulf. The rain-chart plainly shows that the water raised from the heated Gulf is mainly carried northward and eastward. It is this which has given us the Atlantic forest region ; and it is the limitation of this which bounds that forest at the west. The line on the rain-chart indicating twenty-four inches of annual rain is not far from the line of the western limit of trees, except far north, beyond the Great Lakes, where in the coolness of high latitudes, as in the coolness of mountains, a less amount of rainfall suffices for forest growth.
We see, then, why our great plains grow bare as we proceed from the Mississippi westward; though we wonder why this should take place so soon and so abruptly as it does. But, as already stated, the general course of the wind-bearing rains from the Gulf and beyond is such as to water well the Mississippi Valley and all eastward, but not the district west of it.
It does not altogether follow that, because rain or its equivalent is needed for forest,
68 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol'Vi.
therefore wherever there is rain enough, forest must needs cover the ground. At least there are some curious exceptions to such a general rule—exceptions both ways. In the Sierra Nevada we are confronted with a stately forest along with a scanty rain- fall, with rain only in the three winter months. All summer long, under those lofty trees, if you stir up the soil you may be choked with dust. On the other hand, the prairies of Iowa and Illinois, which form deep bays or great islands in our own forest- region, are spread under skies which drop more rain than probably ever falls on the. slopes of the Sierra Nevada, and give it at all seasons. Under the lesser and brief rains we have the loftiest trees we know; under the more copious and well-dispersed rain, we have prairies, without forests at all.
There is little more to say about the first part of this paradox, and I have not much to say about the other. The cause or origin of our prairies—of the unwooded dis- tricts this side of the Mississippi and Missouri—has been much discussed, and a whole. hour would be needed to give a fair account of the different views taken upon this knotty question. The only settled thing about it is that the prairies are not directly owing to a deficiency of rain. That the rain-charts settle, as Professor Whitney well insists.
The prairies which indent or are inclosed in our Atlantic forest-region, and the— plains beyond this region, are different things. But, as the one borders—and in Iowa and Nebraska passes into—the other, it may be supposed that common causes have influenced both together, perhaps more than Professor Whitney allows.
He thinks that the extreme fineness and depth of the usual prairie soil will account tor the absence of trees; and Mr. Lesquereux equally explains it by the nature of the soil, in a different way, These, and other excellent observers, scout the idea that im- memorial burnings, in autumn and spring, have had any effect. Professor Shaler, from his observations in the border land of Kentucky, thinks that they haye—that there are indications there of comparatively recent conversion of oak-openings into prairie, and now—since the burnings are over—of the reconversion of prairie into woodland.
I am disposed, on general considerations, to think that the line of demarcation be- tween our woods and our plains is not where it was drawn by nature. Here, when no physical barrier is interposed between the ground that receives rain enough for forests, and that which receives too little, there must be a debatable border, where comparatively slight causes will turn the scale either way. Difference in soil and difference in exposure will here tell decisively. And along this border, annual burn- ings—for the purpose of increasing and improving buffalo feed—practiced for hun- dreds of years by our nomade predecessors, may have had a very marked effect. I suspect that the irregular border line may have in this way been rendered more irregu- lar, and have been carried farther eastward wherever nature of soil or circumstances of exposure predisposed to it.
It does not follow that trees would re-occupy the land when the operation that de- stroyed them, or kept them down, ceased. The established turf or other occupation of the soil, and the sweeping winds, might prevent that. The difficulty of reforesting bleak New England coasts, which were originally well wooded, is well known. It is equally but probably not more difficult to establish forest on an Iowa prairie, with proper selection of trees.
The difference in the composition of the Atlantic and Pacific forests is not less marked than that of the climate and geographical configuration to which the two are respectively adapted.
With some very notable exceptions the forests of the whole northern hemisphere in the temperate zone (those that we are concerned with) are mainly made up of the same or similar kinds. Not of the same species; for rarely do identical trees occur in any two or more widely separated regions. But all round the world in our zone the woods contain Pines and Firs and Larches, Cypresses and Junipers, Oaks and Birches, Willows and Poplars, Maples and Ashes, and the like. Yet with all these family like-
No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 69
nesses throughout, each region has some peculiar features—some trees by which the country may at once be distinguished. 1
Beginning by a comparison of our Pacific with our Atlantic forest, I need not take the time to enumerate the trees of the latter, as we all may be supposed to know them, and many of the genera will have to be mentioned in drawing the contrast to which I invite your attention. In this you will be impressed most of all, I think, with the fact that the greater part of our familiar trees are ‘‘ conspicuous by their absence” from the Pacific forest.
For example, it has no Magnolias, no Tulip-tree, no Papaw, no Linden or Basswood, and is very poor in Maples; no Locust-trees—neither Flowering Locust nor Honey Locust—nor any leguminous tree ; no Cherry large enough for a timber-tree, like our wild Black Cherry ; no Gum-trees (Nyssa nor Liquidambar), nor Sorrel-tree, nor Kalmia; no Persimmon or Bumelia; nota Holly; only one Ash that may be called a timber-tree; no Catalpa or Sassafras; not a single Elm nor Hackberry; not a Mulberry, nor Planer- tree, nor Maclura; not a Hickory, nor a Beech, nora true Chestnut, nor a Hornbeam ; barely one Birch-tree, and that only far north, where the differences are less striking. But as to coniferous trees, the only missing type is our Bald Cypress, the so-called Cypress of our southern swamps, and that deficiency is made up by other things. But 98 to ordinary trees, if you ask what takes the place in Oregon and California of all these missing kinds, which are familiar on our side of the continent, I must answer, noth- ing, or nearly nothing. There is the Madrona (Arbutus) instead of our Kalmia (both really trees in some places) ; and there is the California laurel instead of our southern Red Bay tree. Nor in any of the genera common to the two does the Pacific forest equal the Atlantic in species. It has not half as many Maples nor Ashes nor Poplars nor Walnuts nor Birches, and those it has are of smaller size and inferior quality ; it has not half as many Oaks; and these and the Ashes are of so inferior economical value that (as we are told) a passable wagon-wheel cannot be made of California wood, nor a really good one in Oregon.
This poverty of the western forest in species and types may be exhibited graphic- ally, in a way which cannot fail to strike the eye more impressively than when we say that, whereas the Atlantic forest is composed of 66 genera and 155 species, the Pacific forest has only 31 genera and 78 species. * Inthe appended diagrams the short side of the rectangle is proportional to the number of genera, the long side to the num- ber of species.
Now the geographical areas of the two forests are not very different. From the Gulf of Mexico to the Gulf of Saint Lawrence about twenty degrees of latitude inter- yene. From the southern end of California to the peninsula of Alaska there are twenty- eight degrees, and the forest on the coast runs some degrees north of this; the length may therefore make up for the comparative narrowness of the Pacific forest region. How can so meagre a forest make so imposing a show? Surely not by the greater number and size of its individuals, so far as deciduous (or more correctly non-conifer- ous) trees are concerned; for on the whole they are inferior to their eastern brethren in size if not in number of individuals. The reason is that a larger proportion of the genera and species are coniferous trees; and these being evergreen (except the Larches), of aspiring port and eminently gregarious habit, usually dominate where they occur. While the East has almost three times as many genera and four times as many species of non-coniferous trees as the West, it has slightly fewer genera and almost one-half fewer species of coniferous trees than the West; that is, the Atlantic coniferous forest is represented by 11 genera and 25 species; the Pacific by 12 genera
* We take in only timber trees, or such as attain in the most favorable localities to a size which gives them a clear title to the arboreous rank. The subtropical southern extremity and keys of Florida are excluded. So also are one or two trees of the Ar- izonian region, which may touch the evanescent southern borders of the Californian forest. In counting the coniferous genera, Pinus, Larix, Picea, Abies, and Tsuga are admitted to this rank, but Cupressus and Chamcyparis are taken as one genus.
70 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [ Vol. VE.
and 44 species. This relative preponderance may also be expressed by the diagrams, jn which the smaller inclosed rectangles, drawn on the same scale, represent the con- iferous portions of these forests.
Indeed, the Pacific forest is made up of conifers, with non-coniferous trees as occa- sional undergrowth or as scattered individuals, and conspicuous only in valleys or in the sparse tree-growth of plains, on which the oaks at most reproduce the features of the ‘‘oak openings” here and there bordering the Mississippi prairie region. Perhaps the most striking contrast between the West and the East, along the latitude usually traversed, is that between the spiry evergreens which the traveller leaves when he: quits California, and the familiar woods of various-hued round-headed trees which give him the feeling of home when he reaches the Mississippi. The Atlantic forest is. particularly rich in these, and is not meagre in coniferous trees. All the glory of the: Pacific forest is in its coniferous trees. Its desperate poverty in other trees appears in the annexed diagram.
RoE ENN ieee) ie 1. 2. 3. 4. 1. Atlantic American forest. 3. Japan-Manchurian forest. 2. Pacific American forest. . 4. European forest.
These diagrams are made more instructive, and the relative richness of the forests. round the world in our latitude is most simply exhibited, by adding two or three simi- lar ones. Two will serve, one for Europe, the other for Northeast Asia. A third would be the Himalay-Altaian region, geographically intermediate between the other two as the Arizona-Rocky Mountain district is between our eastern and western. Both are here left out of view, partly for the-same, partly for special reasons pertaining to each, which I must not stop to explain. These four marked specimens will simply and clearly exhibit the general facts.
Keeping as nearly as possible to the same scale, we may count the indigenous forest trees of all Europe at 33 genera and 85 species, and those of the Japan-Manchurian’ region, of very much smaller geographical area, at 66 genera and 168 species. I here include in it only Japan, Eastern Manchuria, and the adjacent borders of China. The known species of trees must be rather roughly determined, but the numbers here given are not exaggerated, and are much more likely to be sensibly increased by further knowledge than are those of any of the other species. Properly to estimate the sur-. passing richness of this Japan-Manchurian forest, the comparative smallness of geo- graphical area must come in as ah important consideration.
No.1.] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 7T1
To complete the view, let it be noted that the division of these forests into conifer- ous and non-coniferous is, for the— Genera. Species.
Iimopean) DOD-COMMELOUS Pasa uer ath sevens. <2\- 2 45-420 ence ae oe bcmeme eames 26 68 BIO PE Ally COMMON GUS meena pete eter alate aratais me =)ele © H/-) syne oat oja (cyclase eer eras 7 17 33 85
- Japan-Manchurian non-coniferous ......--.-..---2-.---seesceeeee---- AT 123 Danan ManchnriainiCOMIMEPOUS se e\riciinm s)--\e+)-n 2 scncee---cciiatisase 2-2 AO 45 66 168
In other words, a narrow region in Eastern Asia contains twice as many genera and about twice as many species of indigenous trees as are possessed by all Europe; and as to coniferous trees, the former has more genera than the latter has species, and over twice and a half as many species.
The only question about the relation of these four forest regions, as to their com- ponent species, which we can here pause to answer, is to what extent they contain trees of identical species. If we took the shrubs, there would be a small number, if the herbs, a very considerable number, of species common to the two New World and +o the two Old World areas, respectively, at least to their northern portions, even after excluding arctic-alpine plants. The same may be said, in its degree, of the North European flora compared with the Atlantic North American, of the Northeast Asiatic compared with the northern part of the Pacific North American, and also in a peculiar way (which I have formerly pointed out, and shall have soon to mention) of the North- eastern Asiatic flora in its relations to the Atlantic North American. But as to the forest trees there is very little community of species. Yet this is not absolutely wanting.