m 
INTRODUCTION. 21 
tinct. It has a very compact, symmetrical form. The young individuals present a regularly 
oval mass of foliage, which, reaching the ground, completely conceals the stem and branches, 
Older plants attain a height of from 25 to 40 feet, and show a short trunk which supports a 
rounded head. This species bears an edible nut, which is collected by the Indians as an article 
of food. 
Besides the pines, the other Coniferc are Abies Douglasii and Thuja occidentalis. 
We always find upland -oaks associated with the pine growth of this region. These include 
the common Quercus agrifolia and Q. densiflora, the latter species being the more common upon 
the higher ridges. It is of stocky habit, and has wide-spreading branches, which form large 
spherical heads. The bark of this tree appears like that of the elm, and the wood is close- 
grained and durable. 
There is another oak, which has deciduous leaves, the two preceding ы evergreens. It 
seems to be closely allied to or identical with Q. tinctoria. Of this species there are two varie- 
ties which are only distinguishable by the fruit, which in one has a large and prominent 
gland, while in the other the gland is almost concealed by the cup—characters which seem to be 
constant in the same individuals. 
The shrubbery of this region presents but little variety, and consists mostly of species which 
have been enumerated as belonging to the Lower Mountain district. 
We naturally expect to find here the undergrowth which, in &ll countries, accompanies the 
pine forest. Here, indeed, grows the woodland strawberry, (Fragaria vesca,) while liliaceous 
plants are represented by Cyclobothra alba; we also meet with Viola lobata, a recently described 
species of Bentham. But of Orchidacec, so common elsewhere in such localities, we have only 
a solitary species of Platanthera. Curices are sparsely distributed, and Potentilla, so common 
in northern latitudes, has a place in our catalogue. Тһе well-watered valleys are covered with 
a fine sward of native grasses, and lichens of sparkling yellow decorate the decaying pines. 
VEGETATION OF THE EASTERN SLOPE OF THE MOUNTAINS, THE DESERT, AND THE BASIN OF THE COLORADO, 
The features which vegetation presents, within the limits of this section, may be best de- 
scribed by noticing tbose which would naturally attract the attention of the traveller. The 
vegetation of the summit ridge differs but little upon its eastern and western side; but as we 
go further down the abrupt eastern descent a new group of plants comes into view, one which 
presents a marked contrast to that occupying the corresponding Lower Mountain region of the 
Pacific side. Here thorny shrubs and stiff-stalked plants of strange aspect meet.the eye. The 
ashen colored mountains, which in the distance seem entirely destitute of vegetation, produce in 
their rocky cations and crevices a great variety of singular forms. Cacti again appear, and, 
except in one or two instances, are all different from those found on the Pacific slope. There 
are several Opuntias, both those with cylindrical and those with elliptical stems. The gigantic 
Echinocactus cylindraceus lifts its bristling trunk from the clefts of the rock, and the humbler 
mamillaries are also met with. A new species of Cereus (C. Engelmannii) grows in these — 
ties, and bears a deliciously palatable fruit. 
On the upland plains, near the edge of the desert, we find a beautiful shrub with willow-like 
foliage and trumpet-shaped flowers. This showy plant is Chilopsis linearis. Неге we also 
encounter a species of Krameria, having long and spiny branches and deep purple flowers, and 
