CACTUS. The most precious thing in the desert is water, and each desert species of animal or plant has through ages worked out its own answer to the question, " How can I live with so little to drink?" The cactus' answer to this question is very interest ing. Leaves on plants which grow under ordinary conditions are very wasteful of water, taking it up from the sap and giving it out to the air in a process called transpiration. To avoid this waste of water, the cactus has given up having leaves, and has its stems of such form as to expose as little surface as possible to the direct rays of the sun which act to make the plant give up its moisture. Also the stems are thick so as to give room for storage of the precious water and protected with thick covering to keep it safely hoarded.
There are many forms of cacti (as the plural is written) in the United States. The most impressive is the " giant cactus" of Arizona belonging to the genus Cereus. Its stems and branches are like huge spiny columns from one to two feet thick. It often grows 40 or 50 feet high and looks like a giant candlestick. This cactus has long, tubular, very showy flowers.
The fruit is egg-shaped and has a crimson pulp which the Indians use for food ;• they gather it with a forked stick attached to a long pole. Wood peckers find the big stems of this cactus a favorable place for digging out their nests.
Some cacti are in the form of very spiny globes. Those with flat stems belong to the genus Opuntia, a good example of which is the common " prickly pear." Of these there are many species, but they are all alike in having their stems and branches in roundish flattened sections and jointed. They have small fleshy leaves which fall off, and at the base of each is left a tuft of cruel spines of two sorts, meant for the punishment of any thirsty trespasser. The prickly pear has yellow or reddish showy flowers, and a pear-shaped fruit which is delicious and satisfying to thirst. Certain species of Opuntia, which were introduced into Australia as a pretty flowering hedge, have run wild and become " the world's great est vegetable terror," spreading their vicious thorny plants over miles and miles of valuable grazing and farming lands.
Cacti are found native chiefly in the arid regions of America—in Arizona, New Mexico, Central America, and extending to southern South America. About 1,000 species have been named, varying greatly in form and size. Many curious and beautiful varieties are prized as hothouse plants, among them the " night-blooming cereus," whose lovely waxlike blossoms open in a single night and wither at the approach of sunlight.
From the juicy stems of the cactus primitive peoples long ago learned to distil both medicines and intox icating drinks. It was long known that were it not for the prickly spines the cactus would furnish excel lent fodder for cattle, and Luther Burbank spent many years in experimentation to produce a spineless cactus.
Scientific name of giant cactus, Cereus giganteus; a com mon species of edible prickly pear is the Opuntia engelmanni; the globe cactus is Echinocactus horizonthalonius.