328 M 01 -pho genetic Factors 



( 1934 ) grew trees in pots and found that, by adding a small amount of 

 salt to the soil, leaves like sun leaves were formed by the plant. Light, 

 however, probably has a share in the production of xeromorphy, for 



Fig. 14-2. Effect of environment on leaf structure. Sections of leaves of Acer saccharum 

 from 1, south periphery of the tree; 2, center of crown; 3 and 4, base of crown. Various 

 factors are doubtless involved in these changes, but differences in rate of transpiration 

 ( higher in exposed leaves than in the others ) seem especially important. ( From 

 Hanson. ) 



bright light has been shown to reduce leaf area and to increase blade 

 thickness. The xeromorphy observable in many tropical plants may check 

 the harmful effects of too intense insolation. 



Still other factors are probably involved in the development of this sort 



