94 



GROWTH AND WORK OF PLANTS 



to compare the result. The purslane will sometimes grow if it is 

 hung on the fence. It is a kind difficult to kill. Trees and shrubs 

 with thin leaves usually shed them on the approach of winter, 

 since water transpires from them rapidly. Evergreen trees have 

 thick and hard leaves with a strong cuticle. They lose water 



Fig. 84. 



Rhododendron maximum during mild weather in the winter, leaves expanded 

 and extending out laterally in normal position. 



slowly. Interesting observations can be made on rhododendrons, 

 which are often grown in city parks or in private grounds. In 

 extremely cold weather when it is freezing, the rhododendron 

 leaves hang downward and are rolled up into a tube. In this 

 way the leaves lose less water than if they remained flat. It 

 will be remembered that freezing of plant tissue has a drying 

 effect. 



