Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 6, Pt. 3

BOTANY.
surface being, however, covered with thickets of Ceanothits, Purshia, Spircea, Amelanchier,
Cercis, Fremontia, Jianzanita, a low scrub oak, (undescribed,) and a wild plum, (P. subcordata.)
At an altitude of about 3,000 feet we entered a dense forest composed-with the exception of a
single oak, (Q. Kelloggi,)-of coniferous trees, the sugar and yellow pine, Libocedrus, and balsam
fir, all attaining a very large size. At McCumber's, at an elevation of 4,000 feet, the forest
was composed exclusively of coniferous trees, and was, in many places, very dense. The
natural meadows, of which McCumber's fiat is one, are covered with a luxuriant growth of
annual plants, of which I collected nearly a hundred species in a few hours. As a whole,
however, the catalogue does not differ greatly from one which might be made at Fort Reading,
or in Sacramento valley, earlier in the season; but while, at this time, (July 29,) the plains of
the Sacramento were completely dry, and the flowers of spring had long since passed, here
everything was fresh and green, and the meadows were decked with flowers at the period of
their greatest beauty. In the pine forest, the snow berry, (Symphoricarpus,) R?ubts nutkanus,
(a variety of ]. odoratUs.?) and Epilobium angustfolium, grow everywhere, and the ground is
in many places covered with mats of Ceanothus prostratus. Lillies and fritillarias also form a
marked feature of the pine woods here as elsewhere. As we ascended to the summit of the
pass, at an altitude of about 5,000 feet, we left behind us most of the trees which I have
mentioned, and found the forest of the higher portion of our route composed exclusively of the
yellow pine. About the base of Lassen's butte, where, over a large area, the forest had been
burned off, it has been succeeded by dense thickets of Geanothus and Manzanita, and along the
banks of a stream coming down from the snow I noticed a Cornsus, having much the general
aspect of C. Florida, of the eastern States, but evidently quite distinct, (C. pubescens.) On the
eastern slope of Sierra Nevada we found the forests much less dense, and composed of a
smaller number of elements. The yellow pine here formed nine-tenths of all the arborescent
vegetation, and grows to a larger size than on the western side of the mountains. This slope
is evidently not so well watered as the other, and even among the mountains, in various
localities, we found level surfaces, of which the light volcanic soil supported only buncbes of
4rtemnisia and Purshia, with scattered yellow pine trees, outliers of the sage plains, so
characteristic a feature of the region lying east of the mountains.
BOTANY OF THE DISTRICT LYING EAST OF THlE SIERRA NEVADA AND
CASCADE MOUNTAINS.
Descending to the. eastward from the summit of the western range of the Sierra Nevada, we
came into a region of which the geological structure and physical features are fully described in
the geological report. The general monotony of the geological structure of this area finds a
perfect parallel in the simplicity and uniformity of its vegetation. Throughout all the interval
lying between the Cascades and Sierra Nevada and the Rocky mountains, the causes which
have given character to the vegetation have been exceedingly general in their action. The
climate is everywhere characterized by the absence of moisture, which, with the exception of
the mountain summits, which project above the general level, gives to the surface a character to
which the name of desert has not been inappropriately applied. The general aspect of the botany
of this region is made up of three distinct elements. Of these the first is presented by the grassy
plains which border the streams flowing down from the mountains. On these surfaces grows a
considerable variety of annual vegetation, in its general character not unlike that of the Sacramento valley. The second of these botanical phases is that of the sage plains; surfaces upon
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