PLATE IX 



Group of Xerophytes : Cereus giganteus ; to the right Agave Americana, Yucca sp. ; 

 to the left Opuntia sp.; in the background Quercus agrifolia ; on the ground 

 Mesembryanthemum sp. and Sedum sp. (Photograph, Stanford University, Dr. 

 F. M. MacFarland.) 



