254 AGRICULTURAL CHEMISTRY 



nous matter than the stalk. The ash of the stalk is 

 characteristically rich in silica. 



356. Leaves. Since all of the chemical compounds of 

 the plant are first produced in the leaves, and then trans- 

 ported to other parts, it follows that the leaves at different 

 stages of growth have a variable composition. Since the 

 cells of the young leaves contain more protoplasm than 

 mature leaves, the largest amount of nitrogenous matter 

 is present there in the early stages of growth. As the 

 plant matures, this nitrogenous matter is given up for the 

 formation of other parts, and then there is a decline in the 

 percentage amount of nitrogen in the leaves. The largest 

 amount of dry matter in the leaves is found about six 

 weeks before maturity. The plant as a whole, however, 

 increases even more rapidly in dry matter after this 

 time, but no additional organic matter accumulates in the 

 leaves but is used for seed formation. As the plant 

 matures, the total ash in the leaves steadily increases, due 

 to silica, which is deposited there as inert material, while 

 that in the stems declines. As the plant matures, the 

 phosphorus content of the leaves declines, the phosphorus, 

 like the nitrogen, being stored up in the seeds. The 

 largest amount of potash in the leaves is at the time of 

 the largest amount of dry matter, about six weeks before 

 maturity. Next to the seed, the leaves contain the 

 largest amounts of protein, fat, and digestible carbohy- 

 drates of any part of the plant. When green, the leaves 

 have a higher nitrogen content than when yellow. The 

 feeding value of corn fodder depends to a great extent 

 upon the condition of the leaves. 



