346 ORGANIC CHEMISTRY. 



mineral food, and lifts its leaves into the atmosphere, 

 from which it is to derive its principal nourishment. At 

 this point, the true vegetative process commences. 



870. VEGETABLE NUTRITION. Every 



What is the 



office of leaves leaf is a net to catch the fertilizing con- 

 ^ p a stituents of the air, and appropriate them 



to the uses of the plant. It drinks them in through its 

 countless pores, while the root supplies the remaining 

 material and sends it upward in the rising sap. All of 

 these materials meet in the leaf, which is the labora- 

 tory in which their conversion into vegetable matter is 

 to be accomplished. The light and heat of the sun 

 co-operate with the vital forces of the plant, in the 

 transformation which succeeds. 



871. Whatever proportion of carbonic 

 evohed from acid and water may be employed as the 

 plants? raw ma terial, it is obvious, by comparison 



of their composition with that of vegetable substances, 

 as hereafter given, that the oxygen is furnished in 

 larger quantity than is required. Water alone supplies 

 a sufficient quantity of this element, and more than 

 enough for most substances that are to be formed. As 

 the process of transformation proceeds, this gas is there- 

 fore constantly thrown off into the air. It is the refuse 

 of the manufacture. Inasmuch as the evolution takes 

 place from the leaf and other green parts of the plant, 

 it is reasonable to suppose that this is the point where 

 the process of transformation is principally conducted. 

 The gum, sugar, or other materials produced, are dis- 

 solved in the descending sap, and transformed into 

 other products, in the course of their circulation. 



