DESERT PLANTS, such plants as are characteristic of arid regions; in general marked by structures adapted to check transpiration of water, such as reduced leaf surface, absence of leaves, thickened epidermis, hairy or waxy coverings, stomata apparatus)) in sunken pits, the entrances to which may or may not be protected by hairs, perennial underground parts such as bulbs, tubers, rhizomes; and annual plants which flourish during the wet season, where such oc curs, and, like the tops of many of the perennial herbaceous species, die during the dry season. On the other hand water-absorbing organs are often highly developed; the root-systems are not only large but the root-hairs are exceed ingly numerous. Storage organs other than underground parts are common, as in many plants with fleshy leaves and in the thick stems of cacti. In regions of less and less rainfall the vegetation becomes more and more monotonous and restricted to the most resistant forms. In addition to intense heat and light,
drying winds and small rainfall, the plants have often to adapt themselves to withstand salts which are brought to the surface in solution and left as the water evaporates.
Structural differences and similarities may be observed in the plants characteristic of Al pine and Arctic conditions. Another striking character of desert plants is their restriction to a limited area by isolation and by enforced adaptability to peculiar conditions, in which respects desert and Alpine plants are similar, but in which each differ from Arctic plants that have a wide range. See ALPINE PLANTS; ARCTIC REGION ; BEACH PLANTS ; HALOPHYTES; PLANT GEOGRAPHY; XEROPHYTES.