4 PARTMENT OF THE INTERIOK.

2D STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY.
i Vv. HAYDEN, U. S. Geologist-in-Charge.

THE VEGETATION

OF THE

AND

A “COMPARISON WITH THAT OF OTHER PARTS
OF THE WORLD.

BY

ASA GRAY and SIR J. D. HOOKER, F, R. S$.

WASHINGTON, February 11, 1881.

a. ck KY MOUNTAIN REGION,

, ' U
al ai ad id nal aig MR ae ~. Jia, pene

BULLETIN

OF THE

UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY

VoLumME VI. 1880. NUMBER 1.

.

Art. I.—The Vegetation of the Rocky Mountain Re-
gion and a Comparison with that of other Parts
of the World.

By Asa Gray and Joseph D. Hooker.

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
y

!
)
I
THE VEGETATION OF THE ROCKY MOUNTAIN REGION.

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

16GB

Rilo '
cy om

2 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

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 is 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 climatic 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-
Datacrad 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.

_

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, mainl*
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 occupies 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 #bove 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 botanisal districts may be separately investigated.

The smallest in area—since it is restricted to mountain summits and
the least peculiar, is—

IL—THE ALPINE REGION.

Botanically the alpine regions of the temperate zone in the northern
hemisphere are southward prolongations of aretic 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.

)

FY t Py, EA Hy ‘ ) y - i)
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 so: me
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, i. ¢., of the phenogamous portion, under three h vad
- placing the ampler aseley 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 rials of a few isolated summits in New England .
and Northern New York, the Alleghgnian 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 Pacifie 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 (ne 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 author ship.

The left-hand column is so insignificant, that it might have been
omitted. We cannot amplify it by adding Aare 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.

¥
x

Aulantic United States Alpine. Rocky Monntain Alpine. Pacific United States Alpine.

Thalictrum alpinum.

Anemone narcissiflora. Anemone narcissiflora.

Anemone occidentalis (A. Baldensis
Hook).

Ranunculus Eschscholtzii.

Ranunculus pygmeus.

Ranunculus Eschscholtzii.
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. i
Draba crassifolia. | Draba crassifolia.
Draba stellata or muricella. | Draba stellata or muricella.
Draba ventosa, Draba eurycarpa. .

Draba Douglasii.
Draba ......

Solidago humilis, var. alpina.

(Greenland.)

~Gnaphalium supinum.

alpestre.
Lychnis (Melandrium) Kingii.

Silene acaulis.
Cerastium alpinum.

Arenaria verna or vars.
Arenaria Rossii,
Arenaria bitlora.
Arenaria arctica,
pew nivalis. .
ytonia arctica, megarrhiza.

Calandrinia pyymea.
Lrifolium nanum.
- ea godinae.

rifolium dasyphyllum.
Trifolium Parryi.
Astragalus calycosus.
Astragalus alpinus.

po '
yt bide Uralensis, arctica.
tropis nana.
Oxytropis multiceps.

Rubus Chamemorus.
Rubus arcticus.

Dryas octopetala and var.
Geum Rossii.

Potentilla frigida?

Potentilla diversifolia.
Potentilla nivea.

IvEsiA Gordoni.

Sibbaldia procumbens.
Saxifraga adscendens.
Sazifraga Jamesii.
Saxifraga rivularis.
Sazifraga debilis.
ifraga cernua.
Saxifraga Hirculus.
Sazifraga chrysantha.

Saxifraga stellaris.

Saxifraga punctata.
Saxifraga Dahurieca.
Saxifraga nivalis.
ifraga cxspitosa.
Saxifraga bronchialis.
Saxifraga tricuspidata.
Saxifraga flagellaris,
Saxifraga oppositifolia.

Chrysosplenium alternifolinm.

um Rhodiola.
Sedum rhodanthum.
Epilobiam latifolium.

CyMortrevs alpinus.
CYMOPTERUS nivalis.

APLOPAPPUS pygmeus.
ApLopaprus Lyallii.

| Solidago humilis, var. alpina.

TOWNSENDIA cot ta.
TOWNSENDIA Lothrockii,

| Aster andinus.

| Aster alpinus.

Erigeron unitiorum.

Erigeron grandifiorum.
E on ureinum.
radicatum,
maria alpina.

ACTINELLA grandiflora.
ACTINELLA Bra “

Hvrsra algida.
HIvisra nana.

es
‘HE ROCKY MOUNTAIN FLORA

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- ca ws
: by i.

Pacific United States “Alpine,

Smelowskia cal
Thiaspi a

chnis (Mel.) Oalifornica.
+p pl
Cerastium alpinum.
Arenaria verna or vars.

Arenaria biflora.
Arenaria arctica,

Calandrinia pygmea.,

Astragalus alpinus,

Eriogynia pectinata.

Rubus arcticus.
Dryas octopetala.

Potentilla gelida.
Potentilla Breweri.
Potentilla diversifolia.

Potentilla villosa.
IvVEsIA Gordoni.
Ivesia Muirii.
Sibbaldia procumbens.

Saxifraga rivularis.

Saxifraga cernua.

Sazifraga Tolmiei.
Saxifraga stellaris.
Sazifraga bryophora.
Saxifraga punctata.
Saxifraga Dahurica.
Saxifraga nivalis.
Saxifraga ca#spitosa.
Saxifraga broncbialis.

Saxifraga flagellaris.
Saxifraga oppositifolia.
Chrysosplenium alternifoliam.
Sedum Rhodiola.

Epilobium Pe om

| Epilobium obcordatem.

CYMOPTERUS cinerascens.
CymorTEerus Nevadensig.

Aplopaoppus Lyallii.

Erigeron compositum,
Erigeron uniflorum.

Erigeron ursinum.

Antennaria alpina,

é |

he a

Artemisia borealis, L. Sup.

NABALUS nanus.
Nawavus Boottii.

Vaccinium caspitosum.
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.
2
alenmria ebkcnae,

Luzula spicata.
Luzula arcuata.

"Atlantic United States Alpine. Rocky Mountain Mpine.-

|

pe

Artemisia borealis.
Artemisia scopulorum,
Artemisia arctica. |
Senecio Fremonti.
Senecio amplectens.
Senecio Soldanella.
Crepis nana.
Tieracium triste.

Taraxacum levigatum,
Campanula uniflora.

Vaccinium cespitosum.
Arctostaphylos alpina.

Cassiope tetragona.
Cassiope Mertensiana.

Bryanthus empetriformis.

Bryanthus glanduliflorus.
Rhododendron Lapponicum.

Primula angustifolia.
Primula Parry.

Douglasia nivalis.
Douglasia montana.
Androsace Chamejasme,
Gentiana barbellata.
Gentiana tenella.
Gentiana propingua.
Gentiana arctophila.
Gentiana prostrata.
Gentiana glauca.
Gentiana frigida.

Gentiana Parryi.
Phlox bryoides.

Phlox muscoides.

Phlox ceespitosa.

GILia Brandegei.
Polemonium confertum,
Polemonium viscosum.
Polemonium humile.
Eritrichium nanum.
Mertensia alpina.

| CHIONOPHILA Jamesii.

SYNTHYRIS alpina.

Veronica alpina.

Castilleia pallida, var. sept.
Castelleia breviflora.
Euphrasia ofiicinalis (gracilis).
Pedicularis Greenlandica.
Pedicularis Parryi.

Pedicularis secopulorum.
Pedicularis flammea.
Paronychia pulvinata.
Eriogonum androsaceum.

Eriogonum Kingii.
Koenigia Islandica,
Oxyria digyna.

Polygonum viviparum.
Polygonum minimum.
Salix arctica, var.
Salix reticulata.

Salix phlelophyla.

Habenaria obtusata.
Tofieldia palustris.
Tofieldia coccinea.
Lloydia sentina,
Luzula spicata.
Luzula arcuata.

- _ ys ( ? a , e , f
"BULLETIN UNITED STATES GEOLOGI
a |

|
)
)

|
|

Vaccinium caespitosum. —

Cassiope tetragona.
Cassiope Mertensiana.
COassiope pig ore peg
Bryanthus Breweri.
Bryanthus empetriformis.

Bryanthus glanduliflorus.

Primula angustifolia.

Primula suffrutescens.

Androsace Chamejasme.

Gentiana Newberry.

Phlox ceespitosa.
Polemonium confertum.

Polemonium humile.
Eritrichium nanum.

Veronica alpina.
Castilleia pallida, var.

Pedicularis Grenlandica.

Pedicularis ornithorrhyncha.

Briogonum incanum.
Briogonum Lobbdii.
Eriogonum pyrolefolium.

Oxyria digyna.
Polygonum Shastense.
Polygonum viviparum.

Salix arctica, var.
Salix reticulata.
Salix phlelophyla.

Lloydia sentina.
uzula spicata.
Luzula arcuata.

AND HOOKER ON ROCKY MOUNTAIN FLORA. 7

Rocky Mountain Alpine. Pacific United States Alping.

Juncus Parryi. Juneus Parryi.
Juncus Drummond Juncus Drummondii.
Juncus castaneus, Juncus castanens.
Juncus chlorocephalus.
ia scirpina.

Kobres
+ ae Pyrenaica.” Carex Pyrenai
ca. x ca.
Carex gricans. Carex es cans.
Carex scirpoidea. Carex scirpoidea. Carex scirpoidea.
Carex obtusata.
Carex Lyoni.
Carex capitata. Carex capitata.
Carex Breweri.
Carex incurva.

Carex atrata. Carex atrata. Carex atrata.
Carex elpina. Carex alpina.
Carex fuliginosa.
Carex frigida.
Carex feetida. Carex fatida.
Carex lagopina. Carex lagopina.
Carex rigida. Carex rigida.
Carex rariflora. | perce rariflora. *
| Carex podocarp1. _ Carex ocarpa.
Carex capillaris. _ Carex capillans. hil
| Carex filifolia. Carex filifolia.

Carex concinna.

| Carex luzulefolia.
Alopecurus alpinus.

Phleum alpinum. | Phleum alpinum. Phleum alpinum.

| Agrostis rubra, ete.

pean shaeea Pickeringii. )
Hierochloa alpina. Hierochloa alpina.
Trisetum subspicatum. Trisetum subspicatum. Trisetum subspicatum.
Aiva atropurpurea.
Poa laxa. | Poa laxa.
Poa arctica.
Poa oIpina. 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 along 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
Pickeringii ; an orchid, Habenaria obtusata ; a Geum, which has its prinei-
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.
Eriogynia 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. “<a

of these are known to extend to Arctic America. Of the whole 11 tls
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 shor neither to the absolute litte 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 ineluded 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

met
e

= 7 = 7

GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 9

e 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 occurs 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
thoronghly known; that of the Rocky and other western mountains
quite imperfectly so.

IIl.—THE FOREST 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. we

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. Populus balsamifera, L.

——$—

* We are much aided in this account by Prof. C. 8. Sargent’s article on The Forests
of Central Nevada, in Amer. Journ. Sci., ser. 3, xvii, June, 1579, and by his Catalogue

_ of the Forest Trees of North America, 15>0, printed by the United States Census

Bureau.

as

10

Olneya Tesota, Gray.
Parkinsonia Torreyana, Watson.
Prosopis juliflora, DC.

Prosopis pubescens, Benth.
Acacia Greggii, Gray.

Prunus Pennsylvanicay L.
Cercocarpus ledifolius, Nutt.
Pyrus sambucifolia, Cham. & Schl.
Crategus—near rivularis, Nutt.
Amelanchier alnifolia, Nutt.
Cereus giganteus, Engelm.
Sambucus glauca, Nutt.
Arbutus Menziesii, Pursh, var.
Fravinus anomala, Torr.
Fraxinus pistacicefolia, Torr.
Fraxinus viridis, Michx., f.
Chilopsis saligna, Don.
Platanus Wrightii, Watson.
Juglans Californica, Watson.
Juglans rupestris, Engelm.
Quercus Emoryi, Torr.

Quercus hypoleuca, Engelm.
Quercus undulata, Torr.

Betula occidentalis, Hook.

BULLETIN UNITED STATES GEOLOGICAL SURVEY. —

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 Douglasii, Carr.
Picea Engelmanni, Engeln.
Picea pungens, Engelm.
Larix occidentalis, Nutt.
Pinus edulis, Engeln.
Pinus flexilis, James.
Pinus aristata, Engeln.
Pinus Chihuahuana, Engelm. :
Pinus contorta, var. Murrayana, Eng.
Pinus monophylla, Torr. .
Pinus ponderosa, Dougl., var. scopu-
lorum, Engelm. 7
Pinus Arizonica, Engelm.
Yucca brevifolia, Engelm.

This mere botanical enumeration of about fifty species of trees, or at
least arborescent plants, gives no proper idea of 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 — ona
eastern base of the Rocky Mountains to the eastern base of the Sierr:
Nevada and Cascade ranges, and from the Mexican boundary, inrhiiti-
tude 32°, to the northern limit of forest, in about latitude 56°. The
Gialiténes rs 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 arbusecule 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. Arizoniea,
which barely cross the Mexican line; Sapindus marginatus, Arbutus
Menziesii, or what seems to be a mere geographical variety of the
Californian Madrofa, which is not uncommon in Mexico, and which
reaches Southwestern Texas; Fravinus anomala and F. pistaciefolia,

SE

¥ GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. II
Platanus Wrightii, &c., Quercus Emoryi and Q. hypoleuca, &e. 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 Leguminose.

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 trom 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 of 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 unessential 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 a composite species, and
the form of it which we are concerned with, and to which Engelmann

12 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [’ rol VI.

assigns the name of scopulorum (i. e., the Rocky Mountain variet yi is ¥2
the one to which the term “long-leaved” least applies. It is one of the 2
largest trees of the proper Rocky Mountains, along which it ranges from a
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 charae-

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

Y¥ AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 13

ch it abounds at the elevation of 7,500 or 8,000 feet, or rather once
> unded, for, as Professor Sargent states, the trees within reach are
st being cut away to supply the mines with timbering. Tor this pur-
its strong and close- grained, tough, and reddish wood is preferred
oe om of any other available tree.
Pinus monophylla, the single-leaved Nut Pine, is a most characteristie
_ 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 feet in 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
f ehoice it is much used for making charcoal. The great importance of
j

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 Pifon 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-
eaulis) 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 light 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 exception 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

-j, 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 (macrocurpa) 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 — a
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 i? %,

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 54°
and 55°, P. Pngelmanni 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. 4

Picea pungens, as Dr. Engelmann now ealls it, the “Abies Menziesti? =
of Colorado, to the Rocky Mountains of which it is nearly confined,
belongs to an elevational range just beneath that of P. Engelmanni, —
being sparsely associated with Pinus ponderosa, while the latter attends
(and generally dominates) P. contorta, 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 Engelmanni 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-
manw’s identification, into and through the whole length of the Sierra
Nevada, from 8,000 down to 5,000 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 Pacifie coast. In the 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

GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA, 15

nge, as it extends from the Gulf of Saint Lawrence to that of Mexico,
and northwestward into British Columbia, while soutiwestward it
~ yeaches Utah. In the Northern Rocky Mountains it is associated with
J. sabina; 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. It is 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 clesely 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 =

lars of this kind, or the Cottonwoods of the region, are:

Populus monilifera, the Eastern Cottonwood, which reaches the snnnidiesle
slope of the Rocky Mountains, but probably boas not cross them.

Populus Fremonti, a Californian species, a doubtful variety of which
(or perhaps P. Mexicana) is the prevalent Cottonwood of the ine
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 flooring. 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 eleintall 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 adry 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, Q. 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 region, 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.

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. jhe Negundo and Juniperus Virginiana, with Praxinus viridis,
belong to the Atlantic forest region, and do not penetrate far, unless we
count the Californian Vegundo as a derivative form. The connection with
Pacific 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 the 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 @nough 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 along 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, if we
include in the botany of the forest region, not only the plants which are
now sheltered by forest, but those which extend either downward or

2GB

Pa ea
A» m1 8
4

18 BULLETIN UNITED STATES GEOLOGICAL SURVEY. mica

upward over ground which might well nourish the same kind of tree
growth. This is the vegetation of the mountains, as distinguishedl es
that of the high plains.
The peculiar shrubs of the Rocky Mountains (including the Wahsat
Range and corresponding ranges farther north) are only Jamesia pee oY
cana, a Hydrangeous genus of no near affinity to any other, except ee
Fendlera, which (equally unique) belongs to a lower region in New © ie
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 Berbers |
Fendleri, the latter a species of the Vulgaris type. They are all south- —
ern ; thus 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 rotundifolius, Ledum glanduloswm, 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. 8S. 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 Elewagnus 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 ent 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-Ursi, 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

-L] 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 Lewcampyx, 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
2 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 Polemoniacea.

Pentstemon, Castilleia, and Mimulus, of the order Scrophulariacee ; and
Pedicularis here takes its principal American development in the higher
regions.

"s
~
=
‘

4 .
20 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [VolV
Phacelia in Hydrophyllacec, but most of the species are below the fon
est district and of westward range. ‘ at
Eriogonum of Polygonacee, of which the same is to be said, althoug igh
a few species are conspicuous in the wooded region. oe
Composite are very prominent, as they are throughout North Ameri ca, |
and the genus Aplopappus might be added to the foregoing ; but 1 he
most characteristic genera are not in the wooded region. There, to
the species of Solidago and of Aster are less numerous than at the oe -—.
and Prigeron is more prominent than Aster. re
The number of species of Astragalus in the Rocky Mountain aiid mo re f
western districts is inferior only to those of Asia, but they mostly affect *
the unwooded plains. ‘ai ;
Peculiar to and conspicuous in the cooler wooded region are the two |
beautiful long-spurred species of Aquilegia, A. cerulea 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— i
Shepherdia rotundifolia of Parry, in the mountains of Southern Utah.
Peraphyllum ramosissimum, Nutt., a peculiar Pomaceous genus, wee
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.

' JIL—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 below, but they have a good number
of characteristic plants. The prevalent characteristic shrubs are largely
Rosaceous. They are:

Cercocarpus parvifolius, along with C. 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
specie 8.

Cowania Mexicana, which is likewise Mexican, as the name intimates. °

Purshia tridentata, which extends much farther north than the other
but not ascending above = base of the mountains.

L] 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 Great 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 cereum 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 at a 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 Composite are
peculiar to this 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 theGreen 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.vr. :

in the terms employed by Mr. Watson in King’s Exploration (Rep. xxiv,
xxv), which is here accordingly cited: Mi

“ 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 exelu-
sion of nearly all other growth, and 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 tufts 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 trequent 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 obstruct
the way, but very na fiat 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 Eriogona and
Gilie, also several Phacelie and Gnothere, 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 S. Watson, Hydrophyllaceous 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
Pupy Thorn of Lewis and Clark.)

Hermidium, Watson, a Nyctagineous perennial of the western edge of
the basin, intermediate between Bougainvillea and Mirabilis.

Oxrytheca, 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, ef one, de-
pressed Cichoraceous annuals or biennials.

Chetadelpha, Blepharipappus, and Rigiopappus, each of a single species,
and Psathyrotes of two, southern in range, also Composit.

There is, besides, Caulanthus of 8S. 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, 8. Watson, is a peculiar genus of grasses, one species pe-
culiar to the basin, another to the southeastern part of New Mexico.

| * & eee Py. al wl
‘> * li Jit

he Pe

“24 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

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, arather —
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 aiigule little Papaveracea; Petalonyx, in Lousaa
(also Oovallia: which extends both to Texas and Mexico); Hesperocallis,
in Liliacese ; Dithyrwa, which has been joined to the Old World genus
Biscutella ; Wislizena and Oxystylis, in Capparidacee ; Achyronychia,
in lecebracez ; and among Composite the genera Baileya, Riddellia,
Hymenoclea, Hymenothrix ; and here also are the headquarters of ai 7
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” (j. é.,
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 leng
arctic. Southward it is equally broad, and it trends westward and los¢s
itself in the New Mexican plateau region, which has a certain charact
of its own, but in which the eastern forms of vegetation mingle first wi
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 climati¢
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. Suflice 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 séme 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 BuffaloGrass. 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 Archology, in Amer. Jour. Sci., 1878, Ser. 3, xvi, 94,—

-

26 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [VolvVL

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 Chlorideous 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 southern
part of the region, with some 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 ike low and subsaline soils. It is accompanied
by Beckmannta (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
Oallirrhoé ; 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 Gawra, several of G2nothera, 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 Opuntia and Mamillarie), 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; Digelovia and Gutierrezia in charac-
teristic forms which are shared with the ultramontane arid district,
and a great development of Senecionoid Composit, perhaps not exceed-
ing the other parts of the United States, yet more conspicuous to the
eye; the two species of Solanum 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 Crucifere;
Cristatella, in Capparidacer’; Musenium, Polytenia, and Trepocarpus, in
Umbellifere ; Thelesperma (except for a Buenos Ayrean species), Hngel-
mannia, Bradburia, Diaperia, &c., among Composite; Stephanomeria,
Iygodesma and Troximon are aay characteristic i sac age or 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.

ai,

COMPARISON OF THE ATLANTIC, PACIFIC, AND ROCKY MOUNTAIN
REGION FLORAS.

A full and critical.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
tie 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.

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 arctic-alpine flora. And it must 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 Pacifie
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.

RANUNCULACE 2.—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
Olematis (Atragene) verticillaris. All the genera of the Rocky Mountain
flora (if we except Crossosoma) are amphigzan.* Of such genera, Pwonia
is peculiar to the Pacific, and Hepatieca (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 Delphinium 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 2.—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.2:.—Of three genera and as many species in the
Atlantic flora; are equally wanting westward.

BERBERIDACE2Z.—This is a marked family in North America. The
amphigean genus Berberis 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
pecuhar to it and to Northeastern Asia, of single species to each conti-
nent.

NYMPH 2 ACE 2.—Of the typical genera, Nymphcea 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. Nelwmbium has only an Atlantic species, which
even reaches to the West Indies. Srasenia, 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 4.—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.

PAPAVERACEZ.—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,
Stylophorym, 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 Lsechscholtzia, 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-
veraceze form the most characteristic note of the Californian flora.

30 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

Fumanrace.a:.—Three genera, of which only the larger one, Corydalis,

is amphigean. Its species are of Eastern Asiatic rather than European
types and relationship. 0. awrea and its kindred forms, rather than
species extend across the whole continent and to Japan; the striking
species described as OC. 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.

CRUCIFER 4.—lor an order of over 170 genera and more than 2,200
species, North America, in her about 40 indégenous 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 Crucifere 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 it is Physaria,
but the arid region beyond begins to share with California in the abun-
dance of Lepidium, 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.

CAPPARIDACEZ.—Within the limits specified North America has
no Capparee, but all the genera of Cleomece 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, Oristatella, 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 2Z.—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.

VIOLACE2.—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.

POLYGALACE2:.—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.

KRAMERIACE2.—Should be separately reckoned, whatever view be
taken of the affinity of the warm-American (cltiefly 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.

PRANKENIACE Z®.—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 Silenew 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-
sinee, moderately numerous, call for no remark, except for the increased
number of species of Arenaria in the interior flora, most of them peculiar.
Stipulicida is of a single strictly Atlantic species.

ILLECEBRACEZ.—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.

PORTULACACAZ.—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 (Talinopsis), 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 Platine 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.

HyYPERICACE.—Represented by three genera, of which the two —
small ones, Ascyrum and EHlodes, 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.

TERNSTRGMIACE A.—This Eastern 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. Napa 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- ite
cent. Sidalceais peculiar to the Rocky Mountain and Californian floras. 4 |
Ingenhouzia (which is Thurberia) belongs the Western Arizonian flora. *
Malvastrum and Spheralcea (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 | 2
are Mexican. 4
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.—Excepting 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. .

LINACE &.—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 5
even two.

ZYGOPHYLLACE @.—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.

GERANIACEA.—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- — 9
tered over the continent.

LIMNANTHE A.—Are exclusively North American; Limnanthes, of two

5
‘. Le s -

-

No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 33

or three species on the Pacific side, the reduced type Flerkea on the
Atlantic side also; all wanting to the Rocky Mountain flora.

OXALIDE.&.—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.2®.—T wo species of Jimpatiens in the Atlantic States; none
farther westward.

RuvTaAcEeE2.—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 Lan-
thorylum are restricted to the Atlantic border. Cneoridium 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 are represented only in the Atlantic flora by a dozen
species of Jlex and the peculiar monotypic genus Nemopanthes.

CELASTRACE2.—The single Celastrus is restricted to the Atlantic
flora, which has also two species of Euonymus; 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 2.—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.

VITACE2X.—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.

SAPINDACE2.—Most largely tropical, except that there is a Sapindus
along the southern frontiers; are represented only by certain genera.
Four species of sculus characterize the Atlantic flora; one, of a dif-
ferent type, the Pacific flora; and there is none between. Five species
of Acer are peculiar to the Atlantic, two to the Pacifie flora ; one occurs
only in the western Rocky Mountains; one is common to the latter and

3GB

34 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

to the Pacific flora. Negundo, 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) Pacifie

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 Rk. 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.

LEGUMINOSZ.—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 &.—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 Atlantic genera is largely due to genera
which are divided between the Eastern United States and Eastern
Asia, suchas Wistaria, Apios, Amphicarpwa, 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), Prythrina, 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

y

9. 1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 35

1 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.
CRSALPINE.2®.—Excluding 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 Cercis
of its own, rising to the size of a forest tree, also stately trees in @ym-
nocladus and Gleditschia (two species), and of herbs a few species of

MIMOSE4 are in nearly similar case. Not one is truly to be reckoned

in the Pacifie 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 Mimosee (Mimosa, Prosopis in its two forms, Acacia, &c.) char-
acterize the Texano-Mexican bordering district.
- RosacE#®.— 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.

AMYGDALE2®.—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 Pacifie 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, Emplectocladus. Then, the Pacific coast has the curious and
unique genus Nuttallia, Torr. & Gray, which is regularly pluricarpellary.

The trne Rosacee have Spivawa in several types, Neillia, Rubus,

Geum, Fragaria, Potentilla, Aqrimonia, 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 Dalibarda ; to the Pacific tlora, 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 ealled
“Chamiso”) 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 Cercocarpus (with one Mexican species) and the two poten-

36 BULLETIN UNITED simian GEOLOGICAL SURVEY.

tilliform genera or subgenera, kis and Ivesia, the former of onsale
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. 4

Pomp a.—The amphigzean genera or groups, Crategus, Malus, Situ
Amelanchier, extend across the continent at the north, one Sorbus in the
very same species; only Crategus on the Atlantic die 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 4.—Are all North American, except the single Chi-
monanthus of China; two species of Calycanthus peculiar to the Atlantie
flora, one to that of California. i

SAXIFRAGACE®, —An order hardly inferior to Rosacee in extent, in 7.
amount of diversification, and in wideness of distribution. Of the am-
phigeean types, headed by Saaifraga, 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, Tolmiwa, 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.

CRASSULACE.—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 Sedwm, is
of the Atlantic flora. Penthorum, equally peculiar, is of a single species,
restricted to the Atlantic States and to China and Japan.

DROSERACEA:.— 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 Dionewa.

HAMAMELIDE 2.—Are divided between Atlantic North America, South ;
Africa, and Asia (to which most of the genera and species belong) ; our
single Hisauite does not cross the Mississippi; the monotypic Pother-

of eastern range, though it extends into and through Mexico.
HALoRAGE &.—Are of small account. The amphigrean Hippuris and
one or two of Myriophyllum extend across the continent northward ; but
Proserpinaca, of two species, is restricted to the Atlantic flora.
MELASTOMACE &.—Rhevia of the Atlantic flora alone represents this
great typical order in a temperate climate.
~LYTHRACE.&®.—Largely tropical or subtropical; two or three species of
Ammannia and Lythrum are of wide distribution; and the Atlantic States
have a Cuphea anda Neswa, Eastern South American types. The pecu-
liar genus Didiplis is nearly an aquatic Ammannia.
ONAGRACE2.—A largely American order. Epilobium, a cosmopoli-
tan genus, is most diversified in the Pacific flora. Clarkia, Boisduvalia,
Bulobus, Eucharidium, and Heterogaura are restricted to it; Zauschneria,
Gayophytum, and the principal wealth of the great genus G/nothera, to
the Rocky Mountain and Pacific region; Gaura and Stenosiphon mainly
to the great plains east and southeast of the Rocky. Mountains. Lud-
wigia and the diurnal yellow-flowered Ginothere, 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, M/. ornata and
M. nuda, are very characteristic on the plains between the Mississippi
and the Rocky Mountains. Huenide and Petalonyx are Texano-Arizo-
nian genera.
TURNERACE2.—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
Pacific floras. A very few species of Passiflora are indigenous to the
Atlantic States, one extending as far north as Ohio.

CUCURBITACE %.—Are few in this country, and from the interier re-
gion within our proper limits they are absent. The true Hchinocystis is
peculiar to the Atlantic States; two or three species of Megarrhize 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.

DATISCACE &®.—A single Datisca in California, far away from all its
relatives.

CACTACE 22.—Are abundant in and characteristic of the Rocky Mount-
ain region, and still more of the Texano-Arizonian, as of the Mexican
plateau. Twospecies 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 Arizcnian district.

FicoipE 2.—Are extremely few and uninteresting. The early natu-

38 BULLETIN UNITED STATES GEOLOGICAL SURVEY. ol. VI.
ralization and great abundance of Mesembrianthemum on the coast of ;
California is somewhat wonderful. ane
UMBELLIFER2.—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 Pacifie sea-
coast, is also on the coast of Japan. Angelica Ginelini 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.
ARALIACEA.—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 twoin the
Pacific flora; one of them is very close to the Atlantic Aralia racemosa
and is Californian; the other, Hatsia 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, Calli-
fornia only has a species (C. sessilis), of the European and Japanese OC,
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 Kast-
ern Asia. The herbaceous C. Canadensis crosses the continent at the
north, and in Japan meets the allied CO. Suecica. Nyssa, of the Atlantic.
flora, has congeners in the mountains of Asia, while Garrya of the Pacific
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. Triosteum is con-
fined to the Atlantic flora and to Northeastern Asia, with the Himalaya.

ae | eee

No. 1.1 GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 39

Rupracea.—This vast order of over 500 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 Galium

in all, and Cephalanthus is on both sides of the continent and of south-
ern extension. Besides, the Pacitic flora has only the peculiar mono-
typie genus Kelloggia, 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.

VALERIANACE2%.—A small family, is here unimportant. The only
peculiar genus is Plectritis of the Pacific coast and that of Chili.

Composit.a2.— 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 Atlantie 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 &.—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 2.—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 Chrysopsis; the amphigen
genus Frigeron 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

aS

40 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

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.
Baceharis, 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.

HELIANTHOIDE.—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 Silphium, 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!), Engelmannia, most of
Berlandiera, &c.; the Rocky Mountains, Balsamorrhiza, Wyethia, Helian-
thella, &c., which they share with the Pacifie flora; the latter repro-
duces the Coreopsoid type in Leptosyne and Pugiopappus.

GALINSOGE and MADIEa.—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 Madiee,
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. Madia, Layia, and Hemizonia, in numerous spe-
cies, many of them showy, are predominant Composite in California.

HELENIOIDE (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.

ANTHEMIDEA.—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 compose 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 Chenopodiacee, 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-
rotes 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 Pacifie 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 Centaurea 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, Trivis, 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 Liguliflore.—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 Malacothriz; Glyptopleura, Anisocoma,
and mainly Calycoseris are peculiar types in the Great Basin ; and fifteen
species of Malacothriz are peculiar, or nearly so, to the Pacific flora,
which has also Rafinesquia, Apargidium, and Phalacroseris. The paucity
of the large and difficult Old World genus Hieracium in America is a
wonder and a relief to botanists.

LOBELIACE2Z.—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,
Dorwningia, Howellia (an aquatic plant of Oregon), Palmerella, and the
eurious Nemacladus. It has also a peculiar Laurentia, which extends
eastward to the Rocky Mountains, where it is the only representative of
the family.

CAMPANULACE2.—Are not numerous; but Campanula has a few
representatives in all three floras (in the interior only on the mountains),
Npecularia has fewer; and two genera of single species, Githopsis and
Heterocodon, are peculiar to the Pacifie flora.

ERICACE2.—This important order needs to be considered under its
suborders.

VACCINE®.—In the northern hemisphere affect the eastern side of

42 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

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 amphigzean 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 Epigwa (yet with a Japan-
ese counterpart), Oxydendrum, Kalmia, Leiophyllum, and Elliottia, this
shared with Japan. This flora is particularly rich in Andromedee 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 occurs 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 fuil share.

MoONOTROPEZ.—A\|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
Monotropee ; 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 4, 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

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.

PLUMBAGINACE2%.—In this country very few, and confined to the sea-
coasts; are not noteworthy.

PRIMULACE2.—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.

SAPOTACE2.—This is one of several orders which, although mainly
tropical, have temperate representatives in the Atlantic United States,
where there are at least three species of Bumelia.

EBENACE.&.—Are in 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.

STYRACACE.A.—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, Styrav) and eight species; the Pacific
flora only a single Styrax.
~ QOLEACE2.—Are fairly well represented in the Atlantic flora by six
or seven species of Fraxinus, a few of Forestiera, a Chionanthus, and an
Osmanthus ; two species of Fraxinus are the sole representatives in the
Pacific flora. The wide intervening region has none except a Frazxinus,
with simple leaves, on the southern border, where also flourish one or
two species of Forestiera and of the Texano-Mexican genus Menodora.

APOCYNACE 22.—The two species of Apocynum make a part of all three
floras; the Pacific 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.

ASCLEPIADACE 2:—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 inthe 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 Asclepiodora, with tropical parts of America the genus
Buslenia, and is also rich in Gonolobus; and it monopolizes the genera
Podostigma and Anantheriz.

LOGANIACE 42.—As our species of Buddleia and the genus Emorya
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.

GENTIANACE 4.—The Gentians, generally most numerous in mount-
ain districts, preponderate in our western floras; yet the Atlantic States
do not lack species. The amphigean 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. Microcala
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.
FTalenia 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 Pacifie
flora alone belong Draperia and Romanzoffia.

S;ORRAGINACE &.—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 Heliotropium,
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

. -
‘6

+

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-tflowered and showy
Lithosperma of the section Batschia it shares with the plains. The great
genus ot the whole Rocky Mountain flora, though shared with the Pa-
cilfic,is Britrichium ; the characteristic genus of the Pacific 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 WU. 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 seope.

CONVOLVULACE.2.—There are no peculiar genera in North America,
and nothing notable in distribution. There are many more Atlantic
than 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.

SCROPHULARIACEZ.—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 Pentstemon, with
about 4 species at the east and nearly 40 in the Pacific tlora; 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 relatives in Cordylanthus add half as many
more. So Pedicularis, with only 2 Atlantic species, increases westward
to over 20.

OROBANCHACE2.—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

46 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

are wholly Atlantic and one is divided (Aphyllon), the Pacific species nig :
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, also in 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. | |

PEDALIACE@.—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 several in the Texano-Arizonian district.
But the Atlantic flora has an Llytraria 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.

VERBENACEZ.—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 Lippia enter into all three floras. Callicarpa
and Phryma are restricted to the Atlantic flora and toa solitary species.
Both the latter are Eastern Asian, the Phryma in the same species.

LABIATZ.—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
Tsanthus, Cunila, Collinsonia, Conradina, 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.

PLANTAGINACE 2.—Are few in species. Plantago Patagonica, which
abounds on the plains and on the Pacific coast southward, is very poly- _

fe ay Vie 7

ma

GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 4T.

_ 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 Atlantic flora,
abundant in the Texano-Arizonian; are represented by Oxvybaphus on
the plains east of the Rocky Mountains and by Abronia beyond them ;
also by Quamoclidion or Mirabilis with several-flowered calciform invo-
luere. The Great Basin has a peculiar genus, Hermidium of S. Wat-
son, allied to Bougainvillea of South America, but herbaceous.

AMARANTACE 4 (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 Sarcobatvs are the endemic
shrubby genera. Spirostachys is of an extratropical South American
type. Cycloloma and Suckleya ave herbs peculiar to the eastern plains.
PHYTOLACCACE &.—Are represented only in the Atlantic flora, and
by asingle Phytolacca, Rivina belonging farther south.
POLYGONACE2&.—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 Rumer 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 Eriogonee. The genus Eriogonum, 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.
PODOSTEMACE Z.—Aquatic plants of tropical or subtropical rivers,
mostly of the southern hemisphere. A single Podostemdn, on which
the genus and order were founded, belongs to the Atlantic United States.
Its congeners are all in Brazil, Madagascar, and India!
ARISTOLOCHIACE &.—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.
PIPERACE®, 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.

4s BULLETIN UNITED STATES GEOLOGICAL SURVEY.

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.

THYMELAACEA.—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.

ELAHAGNACE A.—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 Hlewagnus belongs to Rocky Mountain region.

LORANTHACEAZ.—Are represented by two genera, allied to Viscwm.
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 amphigzean, of three or four American species, mostly Pacific or south-
ern, one sparingly represented in the Northern Atlantic States.

SANTALACEA.—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—LHremocarpus in the Pacific flora;
Crotonopsis in the Atlantic. Of the Buxine, there is Simmondsia on the
Californian coast, of no near affinity; Pachysandra, in the Alleghanies,
which has a congener in Japan.

EMPETRACE2.—Have all three genera in the Atlantic flora, and not
elsewhere—LEmpetrum alpine and northern ; Corema on the coast of the—
United States, the other species on the opposite Atlantic coast in Por-
tugal; Ceratiola in the Southern Atlantic States.

CERATOPHYLLEA.—Probably of a single species, amphigzean, both
Atlantic and Pacific.

UrTICACEa.—Taken in the large sense, may be referred to under
their suborders.

URTICE®.—Are few'on either side of the continent, nearly absent
from the Rocky Mountains and Great Basin, an Urtiea 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 Eastern Asia. The solitary North American Pilea is confined
to the Atlantic States, and the same of Bahmeria.

No.1.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 49

ULMACE&.—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 42.—The common Hop of the Old World is indigenous in
the Atlantic States and in the Rocky Mountains; the other species is
Chino-Japanese.

Morr &.— 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 2Z.—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 afiinity.

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.

CUPULIFER2%.—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
actessories. 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.

MyRIcacE2.—The amphigean 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 ot
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.

GNETACE Z.—Ephedra, the only extratropical genus, is absent from

4GB

wr?) ee

50 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [V%

ry

the Atlantic flora, has three or four species in the Texano-Arizon: ian
region, two of which enter the Great Basin, and one belongs to the
southern part of California. ; aad ms

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
mountains 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. Thwais of two species, one of the Atlantic
flora, the other of the Pacific and of Japan. Libocedrus is represented
by a peculiar species only in the Pacific flora.

TAXODINEZ.—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 Pacific 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 7. Pattoniana or Williamsonii.
Pseudotsuga Douglasii, of the Pacifie 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 2.—Are represented on the Atlantic coast and north of the
Florida paathante 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.

onan
P eG

GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 51

A BAC 24:.—Absent from the whole interior region; represented by
seven genera in the Atlantic flora, of which Peltandra and Orontium
are peculiar, and Symplocarpus, except that it is reproduced in J wpan ;
‘on the Pacific coast only a relative of the latter, Lysichiton, of which the
8 Species occurs in Japan.
etace=, TYPHACE2.—Both nearly the same on the two sides of
the continent.
NATADACE2.—In similar case, except that the Pacific coast adds

— Lilea and Phyllospadin.
ALISMACE2Z.—Not dissimilar, except that the Atlantic flora has sev-
eral species of Sagittaria and the Pacifie only one, but it has the Euro-
pean type of Damasonium.
HYDROCHARIDACEZ.—The Atlantic flora possesses Limnobium and
Vallisneria as well as Anacharis; the Pacific, only Anacharis; the
_ intermediate region none.
BURMANNIACEZ.—Two Atlantic genera and species of South Amer-
ican affinity ; none in the western floras.
ORCHIDACE.—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 amphigzan species. The Atlantic flora
has the peculiar genera Tipularia and Arethusa (but the latter is in
Japan), and some peculiar Habenarice ; the Pacific possesses two Euro-
pean genera, Cephalanthera and Epipactis, but the latter is also in
Texas, and an European 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.
AMARYLLIDACEZ.—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.

H2MODORACEZ.—Three genera, all strictly peculiar to the Atlantic

States.
BROMELIACE Z.—Tillandsia only along the Atlantic coast; one spe-
cies north to Virginia; others in Florida and its northern border.
IRACEZ.—Two peculiar genera in the Atlantic flora or its borders,
besides [ris and Sisyrinchium, which are more numereus in the Pacific
flora; the former along the mountains between.
DIOSCOREACE Z.—A single Dioscorea, in the Atlantic flora only.
_ S$MILACE2.—A dozen species of Smilax in the Atlantic flora; one of

them barely reaches the Rocky Mountains; a single and peculiar species
in California.
ROXBURGHIACEZ.—Croomia, asingle species, in the Southern Atlantic
States; a close congener in Japan; all other relatives Asiatic.
LILIACcE &.—Here taken in the extended sense, are largely represented
(by twenty-four genera) in the Atlantic flora; are not very few in the

2%

4 # Dye a. ae

52 BULLETIN UNITED STATES GEOLOGICAL SURVEY. ([Vol.VE

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, Brodicea and relatives, Leucocrinum, Chlorogalum,
Calochortus, &c., by Yucca, which is also Atlantic, and by the great
development of the genus Alliwm, exceeded only in Northern Asia.

JUNCACEA.—Are numerous and well distributed over the continent,
but require no special remark.

PONTEDERIACEZ.—Tropical aquatics, except the three genera of the
Atlantic flora, one of which (Schollera) reappears in its single species
on the Pacific coast. e

COMMELYNACE.Z.—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 Xyris are characteristic of the Atlantic flora; are wanting to the
others.

ERIOCAULONE A.—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.

CYPERACE&.—The number of species and genera in the Atlantic
flora is nearly double that of the Pacific, and the Rocky Mountain flora.
has few. .

GRAMINE@, which would be well worth a particular analysis, are more
equally divided, at least as to genera. Of these the western floras have
many, chiefly 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, Cteniwm, 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 repre-
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

YRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 53

1e), indicates a feeble representation ; the blank means that the
ors not indigenous to that flora. - Thus, the second, third, and fourth
$ are not represented, so far as we know, in the Rocks ‘Moashain and
@ Pacific floras, i. e., they do not extend westward beyond the Atlantic
> region. The next line declares that the order Berberidace@ is,
COL Sagring the size of the order (in this instance small), richly repre-
| Seaited 3 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. Nymphaacee 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. Sarraceniacee take full capitals in the first
column, not that the species or types are numerous, but because the
féw and remarkable Sarracenias represent the whole order, excepting
two species; one of them is in California, and the Pacific column is en-
tered accordingly, Such a presentation is only approximate, but in a
- general way it tells the story.

pam we

te

Atlantic Flora.’ Rocky Mountain Flora. | Pacific Flora.
Ranunculacee. Ranunculacez. | Ranunculacez.
MAGNOLIACES.

nacex.
- Menispermacee.
BERBERIDACEZ. Berberidacee. Berberidacez.
NYMPH ZACEZ. N——. | Nympheacee.
SARRACENIACE2. | Sarraceniacee.
Papaveracex. Pp. ; PAPAVERACEZ.
Fumariacee. Fumariacee. Fumariacez.
Crucifere. Crucifere. Cruciferez.
idacex, CLEOMEZ. Capparidacez, CLEOMEZ. | Fie Cleomes,
eae saeco
olygalacez. —

. Krameriacee. | K :

. cape pe ) a tip
Caryophyllacez. aryophyllaceez. Jaryophyllaces
ILLECEBRACEZ. Tllecebracez. | Illecebracee.
Portulacacee. PORTULACACEZ. | PORTULACACEZ
Elatinacez. Elatinacez. | Elatinacee.
HYPERICACEZ. | Hypericacee.
Ternstremiacee.

Malvacez. : Malvacezx. Malvacez.

' Bombacez.
Tiliacee.
Linacee. Linacee. Linacem.

Zygophyllacee.
Geraniacee proper. Geraniacee. Geraniacee.
Limnanthez. LIMNANTHEZ.
Orzalidee. Oralidee. Oxzalidece. ,
Balsaminex
Rutacez. |R |R ~
i iy ; ) Celastracee.
Rhamnacez. Rhamnacew# RHAMNACER.
VITACEZ. Vv | Vitacea.
SAPINDACEZ. Sapindaceae. | Sapindacee.
ANACARDIACEZ. Anacardiacee | Anacardiacem.
PAPILIONACEZ. Papilionacer | PAPILIONACE.
Pinez. C : Cc

J Mimosee
Chrysobalanez.

Amygilalex. Amygdalea. | Amygdalea.
Rosacex propriz. Rosacesx. | Rosaces.
Pome. Pomee. | Pome.
CALYCANTHACEZ. Calycanthaces.
SAXIFRAGACE. Sa ex. SAXIFRAGACEZ.
Crassulac Crassulacee. Crassulacex.
Dnoern vcr ) D

Hamamelidex.
ewe .
Aanbcse.
Lythracez.
Onagracex.

Turneracee.
Passifloracex.
Cucurbitacee.
Oactacee.

Ficoidee.
* Umbellitere.
jacex.
Cornacee.
Caprifoliacee.
Rubiacezx.
Valerianacesz.
Vernoniaceez.
Eupatoriacez.
Asteroidex.

Inuloidee.
Helianthoidex.
Galinsogee.

Helenioidee.
Anthemidee.
Senecionidee.
Cynaroidee.
Mutisiacee.
Cichoracee.
Lobeliacez.
Campanulacee.
VACCINE.
ERICINEZE.
PYROLINEX.
MONOTROPEZ.

DIAPENSIACEZ.
Plumbaginaeee.
Primulacee.
Sapotacce.
Ebenacee.
Styracaceex.
Oleacez.
Apocynacee.
Asclepiadacex.
Loganiacee.
Gentianacee.
Polemoniacee.
Hydrophyllacee.
Borraginacee.
Convolvulacee.
Solanacee.
Scrophulariaceex.
Orobanchacee.
Lentibulacee.
Bignoniacez.
Acanthacee.
Verbenaceez.
Labiate.
Plantaginacee.

Amarantacee.
Phytolaccacee.
Polygonacez, proper.
E——

Podostemacee.
Aristolochiacez.
Saururee.
Lauracez.
Thymeleacee.
Bleagnacee.
Loranthacee.
SANTALACE.
Buphorbiacee.
EMPETRACEZ.
Urticeex.
Ulmaceer.
Cannabinew.
Morex.
Platanacesx.
LEITNERIEZ.
JUGLANDACE.
CUPULIFERA,

Atlantic Flora.

Pi
ms
Sen 7
-

¥
H——.

L——.
ONAGRACE.
LOASACE2.

Cucurbitacee.
CACTACE.
Ficoidew.
UMBELLIFER2.

Cornacee.
Caprifoliacee.
Rubiacee.
Valerianacee.

Eupatoriacee.
Asteroidex.
Inuloidee.

soe nthoidez.

Madiee.
HELENIOIDEZ.
Anthemidee.
Senecionidez.
Cynaroidee.
Mutisiacee.
Cichoracez.
Lobeliacee.
Campanulacee.
Vaecinee.
Ericinee.
Pyrolinee.
Monotropee.

P——.
Primulacee.

O——.
Apocynacee.
Asclepiadaceer.

Gentianacez.
POLEMONIACES.

Borraginaceez.
Convolvulacee.
Solanacee.
SCROPHULARIACE2.
OROBANCHACE.
L———.

Bb.
A :
Verbenacee. -
Labiate.
Plantaginacee.
Nyctaginacee.
Amarantacee.

2 __ EEE

POLYGONACE.
ERIOGONE ZS.

Tlwagnacer.
Loranthacee.
Santalacee.
Buphorbiacee.

U
| U .
Cannabinee.

HYDROPHYLLACEZ.

|

. Cucurbitacee.
a

-UMBELLIFERZ.
Araliacee.
Cornaceer.
Caprifoliacee.
Rubiacee.

| Valerianaceer.

Eupatoriacesw.
Asteroidee.
Inuloidee.
Telianthoidee.
G——.
MADIEZ.
HFLENIOIDES.
Anthemidee.
Senecionidee.
Cynaroidee.

-Cichoracee.
LOBELIACE.
Campanulacee.
Vaccinee.
Ericinee.
Pyrolinee.
MONOTROPEZ.
Lennoacez.

Oleacee.
Apocynacee.
Asclepiadacee.
Gentianacee.
POLEMONIACE.
HYDROPHYLLACES..
Borraginacee.
Convolvulacee.
Solanacee.
SCROPHULARIACEX.
pees gr

ID BROP ly EEE Ter CROP
i

A :
Verbenacee.
Labiatz. ~
_ Plantaginacee.
| Nyctaginacee.
Amarantacee.

| POLYGONACES.
| ERIOGONEZ.

Aristolochiacesx.
Saururee.
Lauracee.
Thymeleacee.
Eleagnacee.
Loranthacee.
Santalacee.
Buphorbiacee.

|
| Urticee.

|

}

| Platanacex.

| Juglandacee.
| Cupulifere.

pal a ae

7

AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 55

by Flora. Rocky Mountain Flora. Pacific Flora.

Gnetaceex.
- Taxinez. Ou fo veceme
-Cupressinex. easine. UPRESSINES.
- Taxodinex. ze Taxodines
Abietinex. Abietinee ABIETINEZ
Palmee. Palmee
Aracesz. Aracee
Lemnacez. L——, Lemnacex®
Typhacee. ace®
A——. exe
Hydrocharidacea. H——
Cannacee.
Orchidacez. Orchidaceee Orchidacess
Amaryllidaceez. A—— ¢ Wie i
Hemodoracex.
Tridacez. Tridacee. Iridaces
Roxburghiacexe
. Ss. Smilacee.
i ; LILIACER.
Juncacex. Juncacez. Juncacex2
Eriocaulonez. teen ms
acer. racex.
Graminez. Graminee. Gooniniat

The groups in this tabulation, it will be observed, have not all the
rank of orders. Such as they are, the—
i ee oes. Md a dann ca caseae esas 156
Rocky Mountain flora (in most extensive sense).........--.------ 112
rs re at. . - Main sewer os tes a wae Oe 127
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—
a CSM Ss oa as oc o AEA aw ale oe Siem oes san sen ce 155
Rocky Mountain........... ooh on Pere ae ie
ee nw e.o- Mn eneea tease! aecaer cace=s - 112
As to the numerical extent "respectively, of these three great diviaiolin
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 Phenogamous 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 8S. 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 district; but

i
:
fy |
'
’
Ml
va
A |
‘
|

—p ae

2 re ae

ee

56 BULLETIN UNITED STATES GEOLOGICAL SURVEY. _ > [ea f

for the proper Rocky Mountains and the eastern plains no such summa: oT

is at hand, although Porter and Coulter’s Flora of Colorado has brought — :
together some of the materials. ai

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 roung-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 Statesis, with one exceptian (that of ‘Nae
eastern Asia), much the most dimeesttind, i. €., the richest in genera and
orders, as well as species, of any other ‘omnerate 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 the 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 Phanogamous orders, the Composite, used to be
reckoned as constituting a tenth part of the Phenogamous vegetation

-) he

*

‘RAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 57

world and an eighth part of that of North America. It forms
ne ur @eighth part of the Atlantic flora. It appears to form between
“asixth and aseventh part of the species in the district west of the Rocky
ountains, 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 Vernoniacee.
The Scrophulariacee are tar 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 Polemoniacew 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 Hydrophyllacee are in nearly a similar case; the Borraginacee
approach to it, and so do the Chenopodiacee.
The Lriogonee, 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 Liliacee (in the extended sense), although the At-
lantic 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.

Ill.
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.

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), Illicium parviflorum, some species
of Asimina, all the Nymphwacee of the Atlantic flora, Ascyrwm amplexi-
caule, &e., our Ampelopsis and Vitis bipinnata, Iler Dahoon, a Rhewia,
Oldenlandia glomerata, Houstonia patens, Pterocaulon, Andromeda nitida,
Cyrilla, Sabbatia gracilis, Mitreola petiolata, Lachnanthes 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 seémingly no less indigenous—may be accounted for by the
immigration of men and cattle. This may have been the case with
Senebiera, Pentaceena, Acena trifida, Plectritis (Betkea) samolifolia, Bow-
lesia lobata, Amblyopappus pusillus, Pectocarya, Lastarrica, and the like. |
For Lrodium 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 Eu-
‘a 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
i 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. Trifolium microdon.
Anemone multifida. Hosackia subpinnata.
Myosurus aristatus. Lathyrus maritimus.
Sisymbrium canescens. Hoftmanseggia.
Vesicaria, said to be arctica. Prosopis (Algarobia) julifiora.
. Malvastrum of North American Prosopis (Strombocarpa) sp. aff.
| type. Fragaria Chilensis.
Spheralceaof North Americantype. Lepuropetalon spathulatum (Atlantic
. Modiola multifida (Atlantic). and Chilian).
; Sida (Pseudo-Malvastrum) sulphu- Gayophytum sp.
. rea. (Enothera sp. aff.
| Blatine Americana. (Hnothera dentata.
| Larrea. (@nothera cheiranthifolia.
Rhus § Lithraa. Boisduvalia sp.
Lupinus microcarpus. Godetia sp.
Trifolium Macrai. Mentzelia sp. aff.

=.
1] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 59

Crantzia lineata. Erythraa Chilensis.

Hydrocotyle ranunculoides, &e. Collomia gracilis, &e.

Osmorrhiza. Gilia pusilla.

Galium § Relbuniun. Gilia (Navarretia) involucrata.
Galium § Trichogalium. Gilia laciniata.

Mikania scandens? Phacelia circinata.

—Gutierrezia. : Phacelia (Microgenetes) Cumingii.
Grindelia. Coldenia § Tiquilia.

»*

_ Aplopappus. Britrichium fuloum, &e.
’ Nardophyllum (aff. Bigelovia). Amsinckia angustifolia.
Micropus. Solanum eleagnifolium.

Adenocaulon. Physalis viscosa.

Polymnia. Minulus luteus.

Thelesperma scabiosoides! Orthocarpus australis,
-Madia sativa. (Verbena § Glandularia, &c.)
Jaumea linearifolia. Plantago Patagonica.

_ Lasthenia obtusifolia. Plantago hirtella.

~ Bahia. Plantago maritima (Eu. &c.).
Schkuhria. Oxybaphus sp.
Blennosperma Chilense. Allionia incarnata.

Actinella sp. Spirostachys sp.

Gaillardia (Cercostylis) (Bonaria). Oxytheca dendroidea.

Soliva (North American species im- Chorizanthe sp.

migrated ?). Lastarreia Chilensis (mentioned
Centaurea (Plectocephalus) Chilen- above).

sis. Podostemon.
Microseris pygmea. Lilea subulata.
Downingia pusilla. Scirpus riparius.
Specularia biflora. Scirpus tatora.
Menodora sp. Hemicarpha subsquarrosa.
Primula farinosa. Gramine, several.

Microcala quadrangularis.

Here are near upon 90 species or genera, and almost half of them are
identical with a few proximately related species. Most of them affect
the Chilian side of the continent. One or two are known only on the
eastern side. The most remarkable of these are the Gaillardia and the
Thelesperma, of Buenos Ayres; the former closely related to an equally
_ unomalous Texan species; the latter almost identical with a Texano-Ne-
braskan species. One of the Strombocarpa species of Prosopis, of the
scuthern 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 Lepuropetalon
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.

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 x
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 a
plants were as well placed for southward as for northward retreat.

cy.
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 theactual __
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 betes
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

21.) GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 61

Ss eldom 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-
tie 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 arctic-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—have
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. (VobLVi

to the botany of the northern hemisphere generally. When they ec
to be applied to the theoretical elucidation of the great difforeneatlil
tween the Atlantic and the Pacific floras it will need to be noted tha: 7
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 —
sizetohing 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 ‘Aitlindie 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-oriental 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 ARCHAZOLOGY.

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.

°
y

“GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 63

I n the district we inhabit such interference is so recent that we have little difficulty
conceiving the conditions which here prevailed, a few generations ago, when the
st primeval”—described in the first lines of a familiar poem—covered essentially
adele 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
la ‘g est and almost the richest of the temperate forests of the world. That is, it com-
s a greater diversity of species than any other, except one.
rs aN oe 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
seene. This rim is formed of the Sierra Nevada. Even its eastern slopes are forest-
_ ¢lad 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-
ealyptus 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 Sierra 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 beth 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,

¢

a

64 BULLETIN UNITED STATES GEOLOGICAL SURVEY. — [Tokv

Bia

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. nae %
So much for 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 are nourished 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 for shelter. 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
rain 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 is a 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. .

- 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 rainfall in 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, i. ¢., 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 deuse and
tall forest on the west from treelessness on the east. We may conjecture, also, why
this North Pacific forest is 50 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 rainfall 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 precarions 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 idiosyncracy 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¥r.

able to the Aowelopuient 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 ayailable
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
whieh 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,

)
}

_——-

GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 67

®@
»

_ ate always expected to support forests, at least when not cut off from sea winds by
imterposed 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 Pacifie—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-
lon, 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 trav-
ersing rivers—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 rainfall is 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 froin 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 l.ne 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-bearinug 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,

— a eae ao
a “a
es,

68 _ BULLETIN UNITED STATES GEOLOGICAL SURVEY. — (Vo 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 —
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 ee
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
for 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 have—that —
there are indications there of comparatively recent conversion of oak-openings inte
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-

”

GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 69

lag 1 ghout, each region has some peculiar features—some trees by which the

“county may at once be distinguished.
, 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
faet that the greater part of our familiar trees are ‘‘ conspicuous by their absence” from
the Pacitic 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; not a 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
as 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 insome 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 inspecies. 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-
yvene. From the southern end of California to the peninsula of Alaska there are twenty-
#ight degrees, and the forest on the coast runs some degrees north of this; the length
ay therefore make up for the comparative narrowness of the Pacitic forest region.
How can so meagre a forest make so imposing a show? Surely not by the greater
Dumber 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
Zenera and species are coniferous trees; and these being evergreen (except the
Larches), of aspiring port and eminently gregarious habit, usually dominate where
they oceur. 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 popropentet © by 11 genera and 25 he ea the Pacific by 12 genera

* We take in only timber trees, or suc ra 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
mimitted to this rank, but Cupressus and Chamecyparis are taken as one genus.

70 BULLETIN UNITED STATES GEOLOGICAL SURVEY. — [¥

and 44 species. This relative preponderance may also be expressed by the diag rr
jn which the smaller inclosed rectangles, drawn on the same scale, rice ¢
iferous portions of these forests.
Indeed, the Pacific forest is made up of conifers, with non-coniferous trees as ocea-
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 7
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. sad

a a

a; 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 bere 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 an important consideration.

No.1] GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 71

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.

OCT MRPOUR aiuto pawiah aS lan ols = ose ibd oii cwwad « ¥ denea aces 26 68
ES EE ee eee ee Peer ee er ee 7 17
33 85
Japan-Manchurian non-coniferous ............ 22.22... - eee eeeeee---- AT 123
Japan-Manchurian coniferous... 2 2....0..- 10.250 ck eece eee ee ecee. eee 19 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
to 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.
The Red Cedar (Juniperus Virginiana) among coniferous trees, and Populus tremuloides
among the deciduous, extend across the American continent specifically unchanged,
though hardly developed as forest trees on the Pacific side. There are probably, but
not certainly, one or two instances on the northern verge of these two forests. There
are as many in which eastern and western species are suggestively similar. The Hem-
lock-Spruce of the Northern Atlantic States and the Yew of Florida are extremely like
corresponding trees of the Pacific forest. Indeed, the Yew-trees of all four regions
may come to be regarded as forms of one polymorphous species. The White Birch of
Europe and that of Canada and New England are in similar case, and so is the com-
mon Chestnut (in America confined to the Atlantic States), which, on the other side

of the world, is also represented in Japan. A link in the other direction is seen in
one Spruce-tree (called in Oregon Menzies Spruce) which inhabits Northeast Asia,
while a peculiar form of it represents the species of the Rocky Mountains.

But now other and more theoretical questions come to be asked, such as these :

Why should our Pacific forest region, which is rich and in some respects unique in
coniferous, be so poor in deciduous trees ?

Then the two Big-trees, Sequoias, as isolated in character as in location—being
found only in California, and having no near relatives anywhere—how came California
to have them?

Such relatives as the Sequoias have are also local, peculiar, and chiefly of one
species to each genus. Only one of them is American, and that solely eastern, the
Taxodium of our Atlantic States and the plateau of Mexico. The others are Japanese
and Chinese.

Why should trees of six related genera, which will all thrive in Europe, be restricted
naturally, one to the eastern side of the American continent, one genus to the western
side and very locally, the rest to a small portion of the eastern border of Asia?

Why should coniferous trees most affect and preserve the greatest number of types
in these parts of the world?

72 BULLETIN UNITED STATES GEOLOGICALSURVEY.

And why should the Northeast Asian region have, in a comparatively small area, not :
only most coniferous trees, but a notably larger number of trees altogether than any _

other part of the northern temperate zone? Why should its only and near rival be
in the antipodes, namely, here in Atlantic North America? In other words, why should
the Pacific and the European forests be so poor in comparison, and why the Pacifie
poorest of all in deciduous yet rich in coniferous trees?

The first step toward an explanation of the superior richness in trees of these an-
tipodal regions, is to note some striking similarities of the two, and especially the
number of peculiar types which they divide between them. The ultimate conclusion
may at length be ventured, that this richness is normal, and that what we really have
to explain is the absence of so many forms from Europe on the one hand, from Oregon
and California on the other. Let me recall to mind the list of kinds (i. e. genera) of
trees which enrich our Atlantic forest but are wanting to that of the Pacific. Now
almost all these recur, in more or less similar but not identical species, in Japan, North
China, &c. Some of them are likewise European, but more are not so. Extending
the comparison to shrubs and herbs, it more and more appears that the forms and types
which we count as peculiar to our Atlantic region, when we compare them, as we first
naturally do, with Europe and with our West, have their close counterparts in Japan
and North China; some in identical species (especially among the herbs), often in
strikingly similar ones, not rarely as sole species of peculiar genera or in related generic
types. I was a very young botanist when I began to notice this; and I have from
time to time made lists of such instances. Evidences of this remarkable relationship
have multiplied year after year, until what was long a Wonder has come to be so com-
mon that [ should now not be greatly surprised if a Sarracenia or a Dionza, or their
like, should turn up in Eastern Asia. Very few of such isolated types remain without
counterparts. It is as if Nature, when she had enough species of a genus to go round,
dealt them fairly, one at least to each quarter of our zone; but when she had only
two of some peculiar kind gave one to us and the other to Japan, Manchuria, or the
Himalayas; when she had only one, divided these between the two partners on the
opposite side of the table. The result, as to the trees, is seen in these four diagrams.
As to number of species generally, it cannot be said that Europe and Pacifie North
America are at all in arrears. But as to trees, either the contrasted regions have been
exceptionally favored, or these have been hardly dealt with. There is, as I have in-
timated, some reason to adopt the latter alternative.

We may take it for granted that the indigenous plants of any country, particularly
the trees, have been selected by climate. Whatever other influences or circumstances
have been brought to bear upon them, or the trees have brought to bear on each other,
no tree could hold its place as a member of any forest or flora which is not adapted to
endure even the extremes of the climate of the region or station, But the character
of the climate will not explain the remarkable paucity of the trees which compose
the indigenous European forest. Thatis proved by experiment, sufficiently prolonged
in certain cases to justify the inference. Probably there is no tree of the northern
temperate zone which will not flourish in some part of Europe. Great Britain alone
can grow double or treble the number of trees that the Atlantic States can. In all
the latter we can grow hardly one tree of the Pacific coast. England supports all of
them, and all our Atlantic trees also, and likewise the Japanese and North Siberian
species, which do thrive here remarkably in some part of the Atlantic coast, especially
the cooler-temperate ones. The poverty of the European sylva is attributable to the
absence of our Atlantic American types, to its having no Magnolia, Liriodendron,
Asimina, Negundo, no ésculus, none of that rich assemblage of leguminous trees
represented by Locusts, Honey-Locusts, Gymnocladus, and Cladrastis (even its Cereis,
which is hardly European, is like the Californian one mainly a shrub) ; no Nyssa, nor
Liquidambar; no Ericacew rising to a tree; no Bumelia, Catalpa, Sassafras, Osage
Orange, Hickory, or Walnut; and as to conifers, no Hemlock Spruce, Arbor-vitz,
Taxodium, nor Torreya. As compared with Northeastern Asia, Europe wants most of

‘

;

_ tthese same types, also the Ailantus, Gingko, and a goodly number of coniferous genera.
ar?! cannot point to any types tending to make up the deficiency; that is, to any not
either in East North Americaor in Northeast Asia, or in both. Cedrus, the true Cedar,
which comes near to it, is only North African and Asian. I need not say that Europe
has no Sequoia, and shares no special type with California.

Now the capital fact is that many and perhaps almost all of these genera of trees
were well represented in Europe throughout the later Tertiary times. It had not
only the same generic types, but in some cases even the same species, or what must
pass as such, in the lack of recognizable distinctions between fossil remains and living’
analogues. Probably the European Miocene forest was about as rich and various as
is ours of the present day, and very like it. The Glacial period came and passed, and
these types have not survived there, nor returned. Hence the comparative poverty
_ of the existing European sylva, or, at least, the probable explanation of the absence
of those kinds of trees which make the characteristic difference.

Why did these trees perish out of Europe, but survive in America and Asia? Before
we inquire how Europe lost them, it may be well to ask how it got them. How came
these American trees to be in Europe? And among the rest, how came Europe to
have Sequoias, now represented only by our two Big-trees of California? It actnally
possessed two species and more—one so closely answering to the Redwood of the coast
ranges, and another so very like the Sequoia gigantea of the Sierra Nevada, that, if
such fossil twigs with leaves and cones had been exhumed in California instead of
Earope, it would confidently be affirmed that we had resurrected the veritable ances-
tors of our two giant trees. Indeed, so it may probably be. ‘‘ Calum non animam
mutant,” &c., may be applicable even to such wide wanderings and such vast inter-
vals of time. If the specific essence has not changed, and even if it has suffered some
change, genealogical connection is to be interred in all such cases.

That is, in these days it is taken for granted that individuals of the same species,
or with a certain likeness throughout, had a single birthplace and are descended from
the same stock, no matter how widely separated they may have been either in space
ortime, or both. The contrary supposition may be made, and was seriously enter-
tained by some not very long ago. It is even supposable that plants and animals
originated where they now are, or where their remains were found, But this is not
science—in other words, it is not conformable to what we now know, and is an asser-
tion that scientific ex planation is not to be sought.

Furthermore, when species of the same genus are not found almost everywhere,
they are usually grouped in one region, as are the Hickories in the Atlantic States,
the Asters and Goldenrods in North America and prevailingly on the Atlantic side, the
heaths in Western Europe and Africa. From this we are led to the inference that all
species closely related to each other have had a common birthplace and origin. So
that, when we find individuals of a species or of a group widely out of the range of
their fellows we wonder how they got there. When we find the same species all round
the hemisphere, we ask how this dispersion came to pass.

Now, a very considerable number of species of herbs and shrubs and a few trees
of the temperate zone are found all round the northern hemisphere ; many others are
found part way round—some in Europe and Eastern Asiaj some in Europe and our
Atlantic States, many, as I have said, in the Atlantic States and Eastern Asia—fewer
(which is curious) common to Pacific States and Eastern Asia, nearer though these
countries be.

We may set it down as useless to try to account for this distribution by causes now in
operation and opportunities now afforded, /. ¢., for distribution across oceans by winds
and currents and birds. These means play their part in dispersion from place to
place, by step after step, but not from continent to continent, except for few things
and in a subordinate way.

Fortunately we are not obliged to have recourse to overstrained suppositions of
what might possibly have occurred now and then, in the lapse of time, by the chance

74 BULLETIN UNITED STATES GEOLOGICAL SURVEY.

conveyance of seeds across oceans, or even from one mountain to another. The plants :
of the top of the White Mountains and of Labrador are mainly the same; but we need
not suppose that it is so because birds have carried seeds from the one to the other.

I take it that the true explanation of the whole problem comes from a just general

view, and not through piecemeal suppositions of chances. And I am clear that it is
‘to ba found by looking to the north, to the state of things at the arctic zone—first, as
it now is, and then as it has been.

North of our forest regions comes the zone unwooded from cold—the zone of arctic
vegetation. In this, as a rule, the species are the same round the world ; as exceptions,
some are restricted to a part of the circle.

The polar projection of the earth down to the northern tropic, as here exhibited,
shows to the eye—as our maps do not—how all the lands come together into one region,
and how natural it may be for the same species, under homogeneous conditions, to
spread over it. When we know, moreover, that sea and land have varied greatly since
these species existed, we may weli believe that any ocean-gaps now in the way of
equable distribution may have been bridged over. There is now only one considera-
ble gap.

What would happen if a cold period were to come on from the north, and were very
slowly to carry the present arctic climate, or something like it, down far into the tem-
perate zone? Why, just what has happened in the Glacial period, when the refrigera-

tion somehow pushed all these plants before it down to Southern Europe, to Middle ~ .

Asia, to the middle and southern part of the United States, and, at length receding,
left some parts of them stranded on the Pyrenees, the Alps, the Appenines, the Can-
casus, on our White and Rocky Mountains, or wherever they could escape the increas-
ing warmth as well by ascending mountains as by receding northward at lower levels.
Those that kept together at a low level and made good their retreat form the main
body of present arctic vegetation. Those that took to the mountains had their line
of retreat cut off, and hold their positions on mountain tops under cover of the frigid
climate due to elevation. The conditions of these on different continents or different
mountains are similar, but not wholly alike. Some species proved better adapted to
one, some to another part of the world. Where less adapted or less adaptable, they
have perished; where better adapted they continue, with or without some change,
and hence the diversification of alpine plants, as well as the general likeness through
all the northern hemisphere.

All this exactly applies to the temperate zone vegetation and to the trees that we
are concerned with. The clew was seized when the fossil botany of the high arctic
regions came to light; when it was demonstrated that in the times next preceding the
Glacial period—in the latest Tertiary—from Spitzbergen and Iceland to Greenland and.
Kamtschatka a climate like that we now enjoy prevailed, and forests like those of New
England and Virginia and of California clothed the land. We infer the climate from
the trees, and the trees give sure indications of the climate.

Thad divined and published the explanation long before I knew of the fossil plants.
These, since made known, render the inference sure, and give us a clear idea of just
what the climate was. At the time we speak of, Greenland, Spitzbergen, and our are-
tic Sea shore had the climate of Pennsylvania and Virginia now. It would take too
much time to enumerate the sorts of trees that have been identified by their leaves
and fruits in the arctic later Tertiary deposits.

I can only say at large that the same species have been found all round the world ;
that the richest and most extensive finds are in Greenland ; that they comprise most
of the sorts which I have spoken of as American trees which once lived in Europe—Mag-
nolias, Sassafras, Hickories, Gum-trees, ouridentical Southern Cypress (for all we can see
of difference), and especially Sequoias, not only the two which obviously answer to the
two Big-trees, now peculiar to California, but several others ; that they equally com-
prise trees now peculiar to Japan and China, three kinds of Gingko-trees, for instance,
ove of tham not evidently distinguishable from the Japan species, which alone sur-

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GRAY AND HOOKER ON THE ROCKY MOUNTAIN FLORA. 75

vives; that we have evidence, not merely of Pines and Maples, Poplars, Birches, Lin-
- dens, and whatever else characterize the temperate-zone forests of our era, but also of
particular species of these, so like those of our own time and country that we may fairly
_ reckon them as the ancestors of several of ours. Long genealogies always deal more
or less in conjecture, but we appear to be within the limits of scientific inference when
we announce that our existing temperate trees came from the north, and within the
bounds of nigh probability when we claim not a few of them as the originals of pres-
entspecies. Remains of the same plants have been found fossil in our temperate re-

gion, as well as in Europe. ;

Here, then, we have reached a fair answer to the question, how the same or similar
species of our trees came to be so dispersed over such widely separated continents. The
lands all diverge from a polar centre, and their proximate portions, however different
from their present configuration and extent, and however changed at different times,
were once the home of those trees, where they flourished in a temperate climate. The
cold period which followed, and which doubtless came on by very slow degrees during
- ages of time, must, long before its culmination, have brought down to our latitudes,
with the similar climate, the forest they possess now, or rather the ancestors of it.
During this long (and we may believe first) occupancy of Europe and the United
States were deposited in pools and shallow waters the cast leaves, fruits, and, occa-
sionally, branches, which are embedded in what are ealled Miocene Tertiary, or later
deposits, most abundant in Europe, from which the American character of the vege-
tation of the period is inferred. Geologists give the same name to these beds in
Greenland and Southern Europe, because they contain the remains of identical and
very similar species of plants, and they used to regard them as of the same age, on
account of this identity. But in fact this identity is good evidence that they cannot
be synchronous. The beds in the lower latitudes must be later,and were forming
when Greenland probably had very nearly the climate which it has now.

Wherefore the high, and not the low, latitudes must be assumed as the birth-place
of our present flora ;* and the present arctic vegetation is best regarded as a derivative
_of the temperate. This flora, which when cireumpolar was as nearly homogeneous
round the high latitudes as the arctic vegetation is now, when slowly translated into
lower latitudes, would preserve its homogeneousness enough to account for the actual
_ distribution of the same and similar species round the world, and for the original en-
dowment of Europe with what we now call American types. It would also vary or
be selected from by the increasing differentiation of climate in the divergent conti-
nents, and on their different sides, in a way which might well account for the present
diversification. From an early period the system of the winds, the great ocean cur-
rents (however they may have oscillated north and south), and the general proportions.
and features of the continents in our latitude (at least of the American continent)
were munch the same as now, so that species of plants, ever so little adapted or pre-
disposed to cold winters and hot summers, would abide and be developed on the east-
ern side of continents, therefore in the Atlantic United States and in Japan and Man-
churia: those with preference for milder winters would incline to the western sides ;
those disposed to tolerate dryness would tend to interiors, or to regions lacking sum-
merrain. So that if the same thousand species were thrust promiscuously into these
several districts, and carried slowly onward in the way supposed, they would inevit-
ably be sifted in sach a manner that the survival of the fittest for each district might
explain the present diversity.

Besides, there are resiftings to take into the account. The glacial period or refrig-
eration from the north, which at its inception forced the temperate flora into our lati-

* This takes for granted, after Nordenskiéld, that there was no preceding Glacial
period, as neither paleontology nor the study of arctic sedimentary strata afford any
evidence of it. Or if there were any, it was too remote in time to concern the present
question.

76 BULLETIN UNITED STATES GEOLOGICAL SURVEY, — [ol.VI.

tude, at its culmination must have carried much or most of it quite beyond. To wl
extent displaced, and how far superseded by the vegetation which in our day borders —
whe ice, or by ice itself, it is difficult to form more than general conjectures—so differ- 7
ent and conlicting are the views of geologists upon the Glacial period. But upon any,

er almost any, of these views, it is safe to conclude that temperate vegetation, such

as preceded the refrigeration and has now again succeeded it, was either thrust out of
Northern Europe and the Northern Atlantic States, or was reduced to precarious ex-
istence and diminished forms. It also appears that, on our own continent at least, a
milder climate than the present, and a considerable submergence of land, transiently
supervened at the north, to which the vegetation must have sensibly responded by a
northward movement, from which it afterward receded.

All these vicissitudes must have left their impress upon the actual vegetation, and
particularly upon the trees. They furnish probable reason for the loss of American
types sustained by Europe.

I conceive that three things have conspired to this loss. First, Europe, hardly ex-
tending south of latitude 40°, is all within the limits generally assigned to severe
glacial action. Second, its mountains trend east and west, from the Pyrenees to the
Carpathians and the Caucasus beyond, near its southern border ; and they had glaciers
of their own, which must have begun their operations, and poured down the north-
ward flanks, while the plains were still covered with forest on the retreat from the great
ice-wave coming from the north. Attacked both on front and rear, much of the forest
must have perished then and there. Third, across the line of retreat of those which
may have flanked the mountain-ranges, or were stationed south of them, stretched the
Mediterranean, an impassable barrier. Some hardy trees may have eked out their ex-
istence on the northern shore of the Mediterranean and the Atlantic coast. But we
doubt not Taxodium and Sequoias, Magnolias and Liquidambars, and even Hickories
and the like were among the missing. Escape by the east, and rehabilitation from
that quarter until a very late period, was apparently prevented by the prolongation
of the Mediterranean to the Caspian and thence to the Siberian Ocean. If we accept
the supposition of Nordenskiéld, that anterior to the Glacial period Europe was
“*bounded on the south by an ocean extending from the Atlantic over the present
deserts of Sahara and Central Asia to the Pacific,” all chance of these American types
having escaped from or re-entered Europe from the south and east is excluded.
Europe may thus be conceived to have been for-a time somewhat in the condition in
which Greenland is now, and indeed to have been connected with Greenland in this
‘or in earlier times. Such a junction, cutting off access of the Gulf Stream to the polar
‘sea, would, as some think, other things remaining as they are, almost of itself give
glaciation to Europe. Greenland may be referred to, by way of comparison, as &
country which, having undergone extreme glaciation, bears the marks of it in the
extreme poverty of its flora, and in the absence of the plants to which its southern
portion, extending six degrees below the arctic circle, might be entitled. It ought to
have trees and might support them. But, since destruction by glaciation, no way has
been open for their return. Europe fared much better, but suffered in its degree in a
‘Similar way.

Turning fora moment to the American continent for a contrast, we find the land
unbroken and open down to the tropic, and the mountains running north and south.
The trees, when touched on the north by the on-coming refrigeration, had only to
move their southern border southward, along an open way, as far as the exigency
required; and there was no impediment to their due return. Then the more southern
latitude of the United States gave great advantage over Europe. On the Atlantic
border proper glaciation was felt only in the northern part, down to about latitude
40°. In the interior of the country, owing doubtless to greater dryness and summer
heat, the limit receded greatly northward in the Mississippi Valley, and gave only
local glaciers to the Rocky Mountains; and no volcanic outbreaks or violent changes
of any kind have here occurred since the types of our present vegetation came to the

——

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- forest trees is one of the consequences.

The still greater richness of Northeast Asia in arboreal vegetation may find expla-
- nation in the prevalence of particularly favorable conditions, both ante-glacial and
recent. The trees of the Miocene circumpolar forest appear to have found there a
secure home; and the Japanese Islands, to which most of these trees belong, must
be remarkably adapted to them. The situation of these islands—analogous to that
of Great Britain, but with the advantage of lower latitude and greater sunshine—
their ample extent north and south, their diversified configuration, their proximity
to the great Pacific gulf-stream, by which a vast body of warm water sweeps along
their accentuated shores, and the comparatively equable diffusion of rain through
out the year, all probably conspire to the preservation and development of an
originally ample inheritance.

The case of the Pacific forest is remarkable and paradoxical. It is, as we know,
the sole refuge of the most characteristic and wide-spread type of Miocene Conifer,
the Sequoias; it is rich in coniferous types beyond any country except Japan; in ite
gold-bearing gravels are indications that it possessed, seemingly down to the very
beginning of the Glacial period, Magnolias and Beeches, a true Chestnut, Liquidambar,
Elms, and other trees now wholly wanting to that side of the continent, though com-
mon both to Japan and to Atlantic North America.* Any attempted explanation of
this extreme paucity of the usually major constituents of the forest, along with a
great development of the minor or coniferous element, would take us quite too far,
and would bring us to mere conjectures.

Much may be attributed to late glaciation;+ something to the tremendous out-
pours of lava which, immediately before the period of refrigeration, deeply covered a
very large part of the forest area; much to the narrowness of the forest belt, to the
want of summer rain, and to the most unequal and precarious distribution of that of
winter. .

Upon all these topics questions open which we are not prepared to discuss. I have
done all that I could hope to do in one lecture if I have distinctly shown that the
races of trees, like the races of men, have come down to us through a prehistoric (or
prenatural-historic) period; and that the explanation of the present condition is te
be sought in the past, and traced in vestiges, and remains, and survivals; that for
the vegetable kingdom also there is a veritable archzxology.

*See especially, Report on the Fossil Plants of the Auriferous Gravel Deposits of
the Sierra Nevada, by L. Lesquereux, Mem. Mus. Comp. Zodlogy, vi, No. 2.—Deter-
mination of fossil leaves, &c., such as these, may be relied on to this extent by the
general botanist, however wary of specific any many generic identifications. These
must be mainly left to the expert in fossil botany. :

+ Sir Joseph Hooker, in an important lecture delivered to the Royal Institution of
Great Britain, April 12, insists much on this.

sco SF te er

“iim init

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