The New Student's Reference Work/Xerophytes

Xerophytes (zēr' ō-fīts), plants adapted to dry soil and air. The conditions of drouth may be occasional, periodic or permanent, and plants have various ways of meeting them. The plan is to avoid as much exposure as possible and to store what water can be obtained. Prominent among drouth adaptations are underground habits (geophilous plants), rolling or folding of leaves, profile position of leaves (compass-plants), motile leaves which can shift their position (sensitive plants), small leaves etc. Probably the most conspicuous feature of plants in permanently dry regions is the organization of reservoirs which retain water and dole it out, according to the need. Such plants, therefore, usually are fleshy or succulent. The xerophytic societies are numerous, and among them may be mentioned rock societies, composed of plants living upon exposed rocks, walls etc.; sand societies, including beaches, dunes and sandy fields; shrubby heaths, in which species of the heath family abound; plains, the great dry areas in the interior of continents; cactus deserts of the southwestern states and Mexico; and tropical deserts, where the drouth conditions are extreme and the vegetation scanty.