DESERT VEGETATION. 



575 



ennials which at the same time develop foliage stems, flowers, and 

 fruit during the rainy season, and then the exposed parts die 

 and the subterranean rootstocks carry the plant through the 



Fig. 5na. 

 Desert society, chiefly cactus, Arizona. (Photograph by Tuomey.) 



dry period. 2d. The plants dependent on ground-water belong 

 to the second category. They are all perennial and have per- 

 ennial aerial shoots. They bloom during the dry cool weather. 



