Page:Popular Science Monthly Volume 51.djvu/659

Rh older plants have been more than a century and a half in growing. The size of the plant is not always a fair criterion of its age, as plants eight to ten feet high, growing from the granite rocks on the southern slopes of the Santa Catalina Mountains, are older than plants four or five times larger growing in deep canons or in yards about the city, where the water supply is not so completely withdrawn. The ability, however, of this plant to withstand prolonged drought is very great. Its enormous mass of succulent tissue, protected by a thick epidermis, enables it to maintain the accumulated moisture for an almost indefinite period, even after every source of outside moisture has been dried up. A plant may be taken up, exposed to the hot, dry air for months, and when replaced in the soil continue to grow, having suffered little apparent injury. Living specimens, weighing several hundred pounds, may be packed in boxes and shipped to Europe and other foreign countries, without injury to their vitality. A few years ago a specimen some eight feet high was placed in the window of one of the Tucson shops. Some eighteen months later it was found on examination to still contain a large amount of moisture. Its vitality is further illustrated by the fact that a foot or more of the top may be cut from the plant in early spring and sent across the continent, flowers developing on the detached portion several weeks after it has reached its destination.

A number of birds, including the Gila woodpecker, the red shafted flicker, and the golden flicker, excavate great holes in the soft tissues in which they build their nests. Later the abandoned