HOW PLANTS DRINK. 57 



special organs. These organs are known as 

 leaves, and are the parts where the chief busi- 

 ness of the plant is transacted. 



A leaf is an expanded mass of cells, containing 

 living green-stuff, supported on a tougher frame- 

 work, or rib-like skeleton. Leaves take in car- 

 bonic acid by means of tiny absorbing mouths, 

 which exist on their upper surface ; and they 

 turn loose most of the oxygen, by the aid of 

 sunlight, building up the carbon into starch, 

 with hydrogen from the water supplied by the 

 roots to them. Leaves are of different shapes, 

 according to the work they have to do for the 

 plant in different situations. Where carbon and 

 sunlight abound they are round, or nearly so ; 

 where carbon and sunlight are scanty, or much 

 competed for, they are more or less divided into 

 minute sections. 



CHAPTER V. 



HOW PLANTS DRINK. 



WE have now learnt that plants really eat for 

 the most part with their leaves. They grow, on 

 the whole, out of the air, not, as most people 

 seem to fancy, out of the soil. Yet you must 

 have noticed that farmers and gardeners think a 

 great deal about the ground in which they plant 

 things, and very little, apparently, about the air 

 around them. What is the reason for this 

 curious neglect of the real food of plants, and 

 this curious importance attached to the mould, 

 or soil they root in ? 



