HOW PLANTS TAKE FOOD FROM AIR 117 



in the air. Millions of them come in contact with 

 the leaf, not only with the edges, as represented 

 in the diagram, but also with the entire surface of 

 the leaf. The leaf then acts as the machine. The 

 sunbeam is the motor power. Thus run, the ma- 

 chine breaks up each molecule of the acid, seizes 

 the atom of carbon, and appropriates it as food 

 for the plant or tree. The two atoms of oxygen, 

 thus liberated, escape back into the air. 



The work done along this line in a season by a 

 single leaf is of course but little. But "many 

 littles make a mickle." The multitude of leaves on 

 the single tree may do a great work for the tree. 

 The ordinary tree of the forest, say, the maple, 

 contains, during the season of growth, as many 

 as four hundred and thirty-two thousand leaves. 

 All combined, they present to the sun a surface 

 of 21,600 square feet, or a half acre. Each one of 

 these leaves is a machine. Each one is separately 

 run by the sunbeam. Each one thus picks out 

 daily from the air, in the season of growth, mil- 

 lions of carbon atoms to feed the tree, four hun 

 dred and thirty-two thousand machines run by sun 

 power, daily doing a mighty work for the growth 

 of the tree. / 



Multiply this number by the infinite multitude 

 of trees in the forests of the whole earth. What 

 a surface power! How great the work done! 

 Millions of tons of carbon daily extracted from 

 the atmosphere, to supply the growth of all the 

 forests. 



