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.
the wild oat. These plants give the gay and varied appearance to the botany of the region,
which has been remarked by all who have visited it at the proper season.
In the valleys of Napa and Sonoma the climate is intermediate in character between that of
the coast and the interior, the extremes of each being tempered to produce a mean in the highest
degree healthful, agreeable, and favorable to the development of vegetation. Here we find,
besides a great profusion of annual plants, the California white oak, (Q. Hindsii,) which grows
solitary or grouped in the manner of the evergreen oak, but attaining a much greater size.
Here also, for the first time, we met with the nut pine, (P. sabiniana,) a tree highly characteristic of the flora of the interior, and generally distributed through the coast mountains back from
the ocean. The Manzanita and several species of Geanothus form shrubby clumps and thickets.
Here, as elsewhere in this region, the lupins, one of which (L. macrocarpus) is shrubby, form a
marked feature in the vegetation. About Benicia, the rounded hills are everywhere covered
with wild oats, and no trees are visible except the evergreen oak, which forms low and limited
groves in the ravines among the hills and on the slopes of Mount Diablo. The shores of
Suisun bay, as well as the borders of the lower Sacramento and San Joaquin rivers, exhibit
wide expanses of tule, (Scirpus lacustris,) which forms in its abundance a striking peculiarity of
the botany of all portions which we visited of California and Oregon. The reasons for the
prevalence of this plant are, however, probably to be found in the imperfect drainage of much
of the surface, rather than in any peculiarities of soil or climate. The low lands bordering the
belt of tule which encircles Suisun bay, are in many places covered and reddened by the Canchalagutta (Erythrea Muhlenbergii.) The botany of Suisun valley exhibits many of the characteristics of that of the valleys of Napa and Sonoma. The soil, which is, for the most part,
derived from the decomposition of sandstone rock, was originally covered with the wild oat,
which here grows in great luxuriance, and with beautiful trees of the Californian white oak,
(Quercus Hindsii.) A large part of the surface is now under cultivation, and at the time we
traversed it was covered with wheat just ready for the reaper. It exhibited a vigorous growth,
and, as I was informed by the farmers, produced from 25 to 50 bushels to the acre; the yield
being greatly affected by the degree in which the great want of the region, that of water, was
supplied.
At Vacaville we left the foot hills of the coast mountains, traversing the valley of the Sacramento diagonally to the foot hills of the Sierra Nevada, near the upper end of the valley. The
rolling surface of the foot hills, on either side of the Sacramento, is covered with wild oat,
scattered trees of the oaks I have mentioned, and, in the more rocky places, the nut pine. The
plain bordering the river exhibits surfaces of different characters, and covered with dihering
vegetation. The upper terrace is frequently gravelly, and sustains a sparse growth of coarse
grasses, of Eryngiunm, llemizonia, Madaria, and other rough or viscous plants; such surfaces
being comparatively sterile and of little value for cultivation. The alluvial plain immediately
bordering the river possesses a fine and fertile soil, and is covered with a dense growth of wild
oat, Artemisia, and other plants. The banks of the streams are lined with belts, of greater or
less width, of timber, which are composed chiefly of the long-acorned oak, (Q. Hindszi,) here
exhibiting a size and beauty of form not surpassed, if equalled, by the oaks of any other part of
the world. Along the water's edge, the sycamore, (P. Nacemosa,) Fraxinus Oregona, the
cotton-wood, (P. Monilifera,) and two species of salix, (S. Hindsiana and S. lasiandra?,) are
overgrown by grape vines, (VFirs Galifornica,) and form a screen, by which the view of the
river is frequently shut out from the traveller upon its banks. At the north end of the valley,
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