HOW PLANTS DRINK. 53 



Let us sum up briefly the main facts we have 

 learned in this long chapter. 



Plants eat carbonic acid under the influence 

 of sunlight. They store up the solar energy thus 

 derived in starches and green-stuff in their own 

 bodies. Very simple plants, which float freely in 

 water, eat and drink with all portions of their 

 surface. But higher plants eat with special or- 

 gans. These organs are known as leaves, and 

 are the parts where the chief business 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 sun- 

 light, 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 car- 

 bon 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 



