XEROPHYTE SOCIETIES. 229 



areas of dry naked soil are sometimes occupied by forest 

 growths which show no development of leaves, the tree-like 

 forms appearing continually bare. The oriental leafless 

 tree form is mostly a Casuarina. Bordering the Gulf of 

 California, both in Mexico proper and in Lower California, 

 there are leafless forests composed of various kinds of 

 giant cactus (see Pig. 187), known as the " cardon forests." 

 These leafless forests represent the most extreme xerophyte 

 conditions occupied by plant forms which may be regarded 

 as trees. 



