LEAVES 



213 



drink. In many such plants the stems or roots are 

 greatly swollen and contain large quantities of water. 

 Leaves also serve as organs for water storage. The 

 thick leaves of century plants are good examples of 

 this kind of leaf. 



Protection ag*ainst loss of water. Plants have many 

 methods of protection against excessive loss of water. 

 One of the most evident methods is in the reduction of 

 the size of the leaves. Plants such as the heaths, 

 which live in very dry soils, have very small leaves. 

 In some desert plants, such as cactuses, the leaves 



Fig. 80. A group of cactus plants. 



are practically wanting. Evaporation is frequently 

 retarded hy modification of the epidermis of the leaves. 



