CHAPTER III 

 THE PLANT 



SECTION XII HOW A PLANT FEEDS FROM 

 THE AIR 



If you partly burn a match, you will see that it becomes 

 black. This black substance is called carbon. Examine a 

 fresh stick of charcoal and estimate how much of a plant 

 is carbon. You see in the charcoal every fiber that you 

 saw in the wood itself. This means that every part of 

 the plant contains carbon. How important, then, is this 

 substance to the plant ! 



You will be surprised to know that all of the carbon in 

 plants comes from the air. All the carbon that a plant gets 

 is taken in by the leaves of the plant. - Not a particle is 

 taken by the roots. 



A large tree, weighing perhaps 11,000 pounds, requires 

 in its growth carbon from 16,000,000 cubic yards of air. 



Perhaps, after these statements, you may think there is 

 danger that the carbon of the air may sometime become 

 exhausted. The air of the whole world contains about 

 1,760,000,000,000 pounds of carbon. Moreover, this is 

 continually being added to by our fires and by the breath 

 of animals. When wood or coal is used for fuel, the 

 carbon of the burning substance is returned to the air in 

 the form of gas. Some large factories burn great quan- 

 tities of coal, and thus turn much carbon back to the air. 



41 



