CHOLLA-CACTUS.
Opuntia prolifera, Engelm. Cactus Family.
Leafless, spiny, arborescent shrubs, three to ten feet high, with elongated, cylindrical joints, covered with oblong tubercles which bear from three to eight spines. Longest spines twelve to eighteen lines long. Stems.—Two to seven inches thick. Flowers.—Purplish-red;
densely clustered at the ends of the branches. Sepals, petals, and stamens, many. Ovary.—One-celled. Style one. Stigmas several. Fruit.—Green; obovate; concave on the top; having no spines, only bristles; usually sterile; often producing other flowers. Hab.—From Ventura to San Diego and southward.
Upon dry hills, even as far north as Ventura, the cholla cactus is a familiar feature of the landscape. In many places it forms extensive and impassable thickets, which afford an asylum to many delicate and tender plants that retire to it as a last refuge from sheep and cattle.
The young joints, which are clustered at the ends of the branches, are from three to nine inches long. By means of their barbed spines, these adhere to any passing object, and as they break off very readily, they are thus often transported to a distance. As they root easily, this seems to afford a means of propagation, in the absence of seed—for the fruit is usually seedless.
The spines are quite variable in length, the longest being sometimes an inch and a half. Each one is covered by a papery sheath, which slips off easily.
Upon the ground about these shrubs may usually be found the skeletons of old branches. These are hollow cylinders of woody basket-work, which are quite symmetrical and pretty.
O. serpentina, Engelm., found at San Diego, and often growing with the above, resembles it somewhat, but may be known by its much longer spines, which are from three to nine inches long, and by its greenish-yellow flowers. The plants are usually found near the seashore and scattered—i.e. never forming thickets.
Upon the sea-coast at San Diego is found another plant similar to the above—Cereus Emoryi, Engelm.—the "velvet cactus." Instead of being covered with tubercles, these plants have from sixteen to twenty vertical ribs, upon which are borne the bunches of slender spines. These spines are from a quarter of an inch to one and three quarters inches long, and without barbs. The flowers are greenish-yellow, and not particularly pretty or attractive.