102 Agricultural Chemistry. 



Amino-acids, which have been referred to as constituents of 

 proteins, occur free to a limited extent in plants. Their struc- 

 ture is that of fatty acids into which amino (NH 2 ) groups have 

 been substituted for hydrogen atoms other than those of acid 

 radicles. They are compounds of only weakly acid or even of 

 basic properties. Amino-valerianic acid is a body of this sort 

 which has been separated from white and yellow lupine plants 

 of two to three weeks' age. Leucin, which is a substituted amino- 

 acetic-acid, occurs in smaller amounts with the amino-valerianic 

 acid. In some coniferous seeds the amount of arginin, another 

 amino acid, exceeds that of the amino acids already mentioned. 

 Arginin is a di-amino acid, that is, it contains two such amino 

 groups. 



Amides are nitrogenous compounds of another class which 

 have been the object of considerable study in their relation to 

 the feeding of animals. The proportion of the total nitrogen in 

 this form at the time of harvesting the plant is of considerable 

 importance because of the probable difference in feeding value 

 of various nitrogenous compounds. Amides have the structure 

 of organic acids, into which amino groups have been substituted 

 for the hydroxyl group of acid radicles. They are, as we might 

 therefore expect, neutral, salt-like bodies. They require only the 

 addition of one part of water to the molecule to become ammo- 

 nium salts, and may be considered as derivatives of ammonia as 

 well as of acids. Asparagin is an amide found in many plants, 

 as in asparagus, peas and beans, especially just after sprouting. 

 Glutamin, which has been found in squash 'seedlings and beet 

 juice with asparagin, is also an amide. These are properly 

 double amino compounds, being amides of amino-acids. They 

 offer examples of the possible complexity of structure of organic 

 nitrogenuous compounds even in their simpler forms. The ami- 

 des and amino-acids which occur at intermediate stages of the 

 growth of plants, are derived from the disintegration of the seed 

 proteins, or from constructive processes in the leaves and are to 



