14 BOTANY. 
fond of an aromatic shrub, of quite a low stature, which grows in considerable quantities on the 
gravelly ridges of both sides of the Colorado. It had shed its seed, but, accidentally, a few 
poor specimens were found—enough to determine it to belong to ambrosie, a sub-division of 
composite. Of this tribe there are in the Eastern States several species, of which cattle and 
horses are very fond. 
The value of the Colorado valley, in affording subsistence to a civilized population, was con- 
sidered nearly equal to that of the Rio Grande valley, which, in some respects, it a good deal 
resembles. The soil is better adapted to the cultivation of cereals than that of the Rio Grande, 
where it can only be done by the assistance of irrigation, which, in this country, is a costly 
process. : 
On leaving the valley of the Colorado, we ascended very rapidly about four thousand feet 
above the level of the sea, where the change of climate is very strongly marked. At the Col- 
orado it is very warm and summer-like, while at our camp (6th Mareh) on the northern slopes 
of the hills and in deep ravines there was snow. Here we met with cedar (Juniperus occiden- 
talis) and pine, (Pinus edulis,) which, however, only greet the eye but a short distance. It may 
be possible that the New Mexican yellow pine (Pinus brachyptera) will be found in still higher 
points of this range in this neighborhood, but, on account of our necessarily rapid movements, 
we had not time to determine. In addition to the trees already mentioned, we noticed here vast 
quantities of the tree Yucca, called by the Mexicans Palma. t was seen before on Bill Williams’ 
fork, but it is found here from twenty-five to thirty-five feet in height, and eighteen inches or 
two feet in diameter, with a bark on the lower part of the trunk very much resembling that of 
white oak. Although not good for fuel, we were sometimes under the necessity of resorting to 
it for camping purposes. Besides these, we saw here a variety of shrubs, the principal of which 
are two species of Rhus, (one of which I had never before seen,) blue-berried Berberis, Cowania 
Stansburiana, Fallugia paradoxa, Shrubby artemisia, Obione, and a shrubby Amygdalus or 
Cerasus, which very much resembles one common on Devil’s river, in lower Texas. A species 
of Chilopsis, a bignoniaceous shrub, or small tree, with beautiful large flowers, much resem- 
bling those of a Catalpa, is frequently found in the dry ravines here, as also all over the western 
wilds. An undetermined species of Lycium, a solanaceous shrub, with an edible berry, was 
also collected here. 
Besides some new cactace, which will be mentioned scon, we found here several species, 
supposed to be peculiar to the Rio Grande valley; among them are Opuntia clavata and 
OQ. fragilis. A flat-jointed Opuntia, with long brown spines, collected before as far back as the 
Llano Estacado, which was considered very near Op. pheacantha of the Rio Grande valley, was 
also found on this part of our route. Also an aggregate Cereus, which cannot be distin guished, 
in the absence of flower and fruit, from allied species on the Rio Grande. Besides the Echino- 
cactus Wislizeni, which is quite common here, we found a new species of the same genus, aggre- 
gated in large globose or ovate heads. 
The fruit is crowned with the dry flower, and is thickly covered with a whitish wool; the 
scales are lanceolate-subulate ; and the seeds pyriform, black, and rugose. The aggregated 
form of this plant is peculiar, and an exception to the general habit of the genus. It had 
already passed flowering, (March 2d,) and matured its fruit. 
After crossing the dividing ridge between the Rio Colorado and Mojave creek, we saw the 
celebrated, but totally useless, Larrea Mexicana, or creosote plant, giving the surrounding 
scenery a most beautiful and verdant appearance. This plant is one of the most repulsive that 
can well be imagined. It is the surest indication of a sterile, worthless soil that can be found 
in the vegetable kingdom ; for wherever it flourishes, little else can be found. 
Section X. Mojave Valley.—This regioneextends from Soda lake to Cajon Pass, a distance of 
about one hundred and thirty miles. With the exception of the last twenty-five miles, it is 
entirely along the Mojave creek. There are beautiful grassy plains in this valley, within reach 
of clear, sweet, running water, where, we were told, it was a great grazing resort for those 
