Fig. 133. — A group of Xerophytes. The ca(;tu.s is Cereus giganteus; absence 

 of leaves and the development of spines are conspicuous. At the right are 

 an agave with broad fleshy leaves and a yucca with harsh, narrow leaves; 

 both have moisture-conserving epidermis. The small plants are Mesembry- 

 unthemum and Sedum, both of which have fleshy leaves for the storage of 

 water and some protective covering, such as hairs or thick epidermis, to 

 aid in its conservation. (From Campbell, after a photograph by Dr. F. M. 

 MacFarland.) 



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