356 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



plant matures. Protein is especially abundant in leguminous 

 plants, and in seeds, particularly the seeds of legumes. The fol- 

 lowing table shows the amounts of protein in some vegetable sub- 

 stances : 



PROTEIN IN VEGETABLE MATERIALS. 



Per cent. 



Corn fodder, green 1.8 



Potatoes 2.1 



Onions 1.4 



Timothy, green 3.1 



Red clover, green 4.4 



Corn, grain 10.5 



Wheat, grain 11.9 



Cowpeas, grain 20.8 



Corn fodder 4.5 



Timothy hay 5.9 



Red clover hay 12.3 



Cowpea hay 16 6 



Soja beans 34.0 



The nitrogenous constituents of agricultural plants may be 

 divided into the four following groups: (i) proteids; (2) amides 

 and amido acids; (3) inorganic compounds; (4) miscellaneous 

 bodies ; which include alkaloids, lecithin, chlorophyll, etc. Pro- 

 teids and amides are of common occurrence in agricultural prod- 

 ucts ; the other bodies, while of some importance, are of less 

 general occurrence. 



Proteids. Proteids are complex bodies of unknown high mole- 

 cular weight and unknown .constitution. They contain carbon, 

 hydrogen, oxygen, nitrogen, sulphur, and sometimes phos- 

 phorus. Proteids are exceedingly important, being necessary 

 to the life of both plants and animals. The flesh of animals is 

 composed largely of proteids, which are derived from vegetable 

 proteids. When split up, proteids yield various amides, amido 

 compounds, and other bodies. This splitting up takes place dur- 

 ing digestion, and the digested constituents are reunited in the 

 animal body to form animal proteids, which are different from 

 the original vegetable proteids. The splitting up also takes place 

 in the germination of seeds, when the reserve proteids are broken 

 up into asparagin and other bodies, and used in the production 

 of new tissue in the growing portions of the plant. 



