The Leaf 123 



so that the air cannot reach them freely, but more 

 frequently the surface of the leaf is diminished. Besides 

 the pines and firs of which mention was made in an 

 earlier chapter the heaths show a good example of this 

 reduction of surface. They live on moors and exposed 

 places where if they had broad leaves the cold dry 

 winds which often sweep over them would make 



Fig. 62. Black Wood of Bannoch, Perthshire, showing Scotch Pine 

 and Ling. 



evaporation go on too quickly and would chill the 

 plants just as you chill your hand if you blow on it 

 when it is wet. This is prevented by the leaf surface 

 being curled over towards the mid-rib, so that the 

 stomata which are on the under side are protected from 

 the wind and can give off moisture as gradually as if 

 the plant grew in a more sheltered position. 



When plants grow on the sea shore, or in marshes 



