PLANT SOCIETIES 
371 
Greek, xeros , dry; phyton, plant). Xerophytes usually 
have long roots so that when moisture is present they may 
gather it rapidly. Many forms have little surface exposed 
to the air; the branches are few, and there are no leaves. 
The stem, which is green in color, performs the work of 
photosynthesis. To conserve their water supply further, 
the xerophytes have a thick epidermis and few stomata (see 
Figure 344. — Giant Cacti — Xerophytes. 
Figure 342). These plants are an admirable illustration of 
making the most of what one has. 
Desert plants live in regions where it is usually both hot 
and dry, but plants of the Arctic Regions have many of 
the same modifications, only in a lesser degree. Much of 
the time severe cold prevents the roots from absorbing 
water, and the plant must keep what it already possesses. 
Some of the Arctic plants, therefore, have leaves which 
roll to reduce the surface and have, in addition, a coating 
of hairs, both devices for retarding transpiration. 
