HOW THE LEAF GETS FOOD FROM THE AIR 79 



blue gum, figure 40) get less sunshine and so lose less 

 water. Desert plants expose only a little surface, 

 having only a few small leaves or none at all. 



FIG. 43. The reach for light of a tree. 



In winter most plants lose their leaves because the 

 roots cannot take up water when it is cold; and so the 

 plant must, as it were, take in sail and make its sur- 

 face smaller. 



What happens if the roots are chilled? Put a vig- 

 orous potted plant in a box. Then pack ice around 

 the pot and fill the box with sawdust. Keep it in this 





