PHANTOM FLOWERS. 75 



acid pervades the atmosphere, from which the leaves 

 are constantly separating it from the oxygen, and ap- 

 propriating its carbon as a continuous contribution to 

 the growth of the plant. The roots, by a process of 

 their own, in like manner extract the same substance 

 from the carbonic acid of the water around and below 

 them, and convey it upward into the body of the plant. 

 But much the largest portion of the carbonic acid 

 which forms the food of plants, is absorbed by the 

 leaves. 



As carbon, and not carbonic acid, is the food of 

 plants, the power of decomposing the latter, so as to 

 leave them in possession of the former, and of expel- 

 ling the superfluous oxygen, is therefore indispensable 

 to their growth. In reality, the leaves are the lungs, 

 as their functions are strikingly analogous to those 

 performed by the lungs of animals. The green leaves 

 of a growing plant absorb carbonic acid ; they expose 

 it to the action of the sun's light ; the oxygen is 

 separated from the carbonic acid, and is given out 

 by the leaves ; the carbon remains, and, entering 

 into the system of the plant, immediately increases 

 its bulk. 



The growth and vigor of the tree depend on the 

 rapidity with which this decomposition, or digestion of 



