This charm was, however, soon to be dispelled. On descending to the plain, it became as usual desirable to find a good situation for an encampment, abounding with grass for the horses, and convenient to a water course. For this purpose, one of the party rode to a small line of timber about a mile on our left, which ran in a parallel direction to our line of march. He overtook us again at the distance of two or three miles, having discovered a copious stream of water. It was about three miles below the point at which the water had been discovered that we gained the line of timber, only to experience the mortification of disappointment in finding a naked bed of sand, the stream having, no doubt, sunk into the earth some distance above. We had, therefore, to undergo the pains of abstinence still longer, until we again sought the timber further below, where the water had reappeared on the surface. [153] Probably one of the branches of Cheyenne Creek.—ED. [154] Cheyenne Mountain(?).—ED. Near this encampment, we first observed the great shrubby cactus[155] which forms so conspicuous a feature in the vegetable physiognomy of the plains of the Arkansa. Its trunk is six or eight feet in height, and at the root five or six inches in diameter. It is much branched, the ultimate divisions consisting of long cylindric articulations. The flowers are as large as those of the C. ferox, of a purple colour, and are placed on the ends of the articulations. These last are arranged somewhat in whorls about the ends of the smaller branches. The surface of every part of the plant, aside from its terrific armature of thorns, is marked by little prominences of near an inch in length, and about one-fourth of an inch in breadth, rising considerably, and bearing a cluster of radiating spines. These are of various lengths, one pointing {209} obliquely upward, being commonly much the largest. At their insertion, these thorns are surrounded by pungent setæ in the manner of C. ferox. The whole plant is so thickly beset with strong spines pointing in every direction, that no large animal can approach it unharmed. It does not form thickets, but each plant is a cluster by itself; and when first seen at a distance, they were mistaken for bisons. We were informed by one of our engagees, who had penetrated the Spanish provinces as far as Monterey, that this plant is common there, and its fruit much esteemed. The nopals are considered characteristic of warm and dry climates, like those of Egypt and California.[156] Perhaps there is no part of the world where plants of this family constitute so large a proportion of the vegetable products of the soil, as in the arid plains of the Arkansa. These plains are sufficiently dry; but like those of the Platte and Upper Missouri, where cacti are almost equally abundant, they are visited by very severe cold in winter. [155] Cactus cylindricus of Humboldt.—JAMES.