New York Agricultural Experiment Station. 37 



IX. The Chemistry of Plants, Plant-foods and Soils. 

 I. The Constituents of Plants, 



Chemical Elements. — All matter is composed of about seventy 

 different chemical elements. A clieinical element is any substance 

 which cannot, hy any Icnown means, he separated into txoo or more 

 different kinds of matter. For example, gold is an element, 

 because, in whatever manner it may be treated, we cannot get any- 

 thing out of it but gold ; pure gold contains nothing but gold. So 

 nitrogen is an element, because, as far as we aljle to find out, it con- 

 tains only one thing, that is, nitrogen. Similarly, carbon, sulphur, 

 potassium, oxygen and iron are elements. 



Just as the twenty-six letters of our alphabet are combined in 

 various ways to form the words of a whole language, so these seventy 

 elements or simple substances, constituting nature's alphabet of mat- 

 ter, are capable of being united to produce all the different chemical 

 compounds that go to make up the countless forms of matter. The 

 number of different combinations possible between these seventy 

 elements is practically infinite. 



Elementary Composition of Plants. — When we state what 

 elements any substance contains, we give its elementary composition. 

 For example, sugar contains the elements, carbon, hydrogen, and 

 oxygen ; this is a statement of the eleinentary composition of sugar. 

 So, when we state what elements a plant contains, we give its ele- 

 mentary composition or analysis. The term idtimate composition 

 means the same as elementary composition. We will now consider 

 the elementary composition of plants. 



The exact number of different kinds of plants growing on the 

 earth has never been definitely ascertained ; but the number prob- 

 ably exceeds 200,000. Of this large nnmber, only a few have been 

 subjected to careful chemical analysis, and yet so uniform in all its 

 great variety are nature's methods of working and building, that we 

 can quite safely say that, so far as the elementary composition of 

 plants is concerned, little remains to be learned. Chemical analysis 

 shows that, of the seventy elem,ents known to exist, only fourteen 

 are essential to p>roduce all the different forms of vegetable life. 



While all plants contain certain chemical compounds in common, 

 such as cellulose, albuminoids, etc., it may be that each plant con- 

 tains in some one or all of its parts one or more chemical compounds 

 peculiar to itself, so that there may be as many distinct chemical 



