XEKOPHYTE ASSOCIATIONS 



191 



Fig. 169. The spring 

 beauty (Claytonia), 



showing subterranean 



tuber-like stem sending leaf and flower-bearing 



stem above the surface. — After Atkinson. 



turn of the moist season 

 these underground parts 

 develop new exposed 

 surfaces. In such cases 

 it may be said that at 

 the coming of the drouth 

 the plant seeks a sub- 

 terranean retreat. 



A little less decrease 

 of exposed surface is 

 shown by the deciduous 

 habit. It is known that 

 certain trees and shrubs, 

 whose bodies remain 

 exposed to the drouth, 

 shed their leaves and 

 thus very greatly reduce 

 the amount of exposure ; 

 with the return of mois- 

 ture, new leaves are put 

 forth. It will be re- 

 marked, in this connec- 

 tion, that the same 

 habits serve just as well 

 to bridge over a period 

 of cold as a period of 

 drouth, and perhaps 

 they are more familiar 

 in connection with the 

 cold period than in con- 

 nection with the drouth 

 period. 



136. Temporary reduc- 

 tion of surface. — While 

 the habits above have to 

 do with regular drouth 



