The Vegetation of North America 



339 



^m.sk. 





■'^m i M 



Fig. 211. 



[^ 5 Cooper 



Desert vegetation on Tonto Platform, Grand Canon, Arizona, consisting of 

 prickly-pear cactus, yucca, and low shrubs. 



and woody perennials. Desert plants are either extreme xero- 

 phytes, or they are mesophytic short-lived annuals that com- 

 plete their life cycle during a single moist period. The xerophytes 

 include those with thick stems that accumulate enough water 

 during the rains to carry them over dry periods, like the shallow- 



S.-r^ *A;* i^*i 



^^i; 



tr. 5. Cooper 

 Fig. 212. A desert shrub, Fouquieria splendens, in leaf, near Tucson, Arizona. This plant 

 is found over wide areas in the Southwestern desert. 



