PART I. 



OF THE CHEMICAL PROCESSES IN THE NUTRITION 



OF VEGETABLES. 



CHAPTER I. 



OF THE CONSTITUENT ELEMENTS OF PLANTS. 



The ultimate constituents of plants are those which 

 form organic matter in general, namely, Carbon, Hy- 

 drogen, Nitrogen, and Oxygen. These elements are 

 always present in plants, and produce by their union 

 the various proximate principles of which they con- 

 sist. It is, therefore, necessary, to be acquainted 

 with their individual characters, for it is only by a 

 correct appreciation of these that we are enabled to 

 explain the functions which they perform in the veg- 

 etable organization. 



Carbon is an elementary substance, endowed with 

 a considerable range of affinity. With oxygen it 

 unites in two proportions, forming the gaseous com- 

 pounds known under the names of carbonic acid and 

 carbonic oxide. The former of these is emitted in 

 immense quantities from many volcanoes and mineral 

 springs, and is a product of the combustion and de- 

 cay of organic matter. It is subject to be decom- 

 posed by various agencies, and its elements then ar- 

 range themselves into new combinations. Carbon is 

 familiarly known as charcoal, but in this state it is 

 mixed with several earthy bodies ; in a state of ab- 

 solute purity it constitutes the diamond.* 



* Wood charcoal contains about l-50th of its weight of alkaline and 

 earthy salts, which constitute the ashes when it is burned. 



