44 



nitrogen. The grain contains a fairly constant percentage of phos- 

 phoric acid after flowering. In 1914 the nitrogen, phosphoric acid 

 and potash in the grain of the autumnal crop were determined at 

 successive stages during maturation, with the following results : 



Table 35, Percentage of Nitrogen, Phosphoric acid 

 and Potash in the Grain. 



These figures show that the percentage of phosphoric acid is 

 much lower at the time of heading out and increases a great deal 

 up to the time of flowering ; afterwards it remains about constant, 

 while the percentage of nitrogen slightly decreases, and that of potash 

 diminishes very markedly. In other words, the amounts of phosphoric 

 acid and nitrogen increase somewhat proportionally to the increase 

 of dry matter in the grain, whereas the amount of potash does not. 

 Hence, it may be presumed that phosphoric acid and nitrogen are 

 very necessary in the grain from the time of heading out till the end 

 of maturity, and that potash plays an important part in the early 

 life of the grain. This leads to the suggestion that phosphoric acid 

 and nitrogen are stored much more in the seed than in the chaff; 

 and also that the potash are very necessary for the formation of 

 chaff, which latter develops when the grain is at a young stage. 

 This will be explained in detail later. 



The total amount of phosphoric acid in the plant increases 

 slowly at an early stage of growth, and rather rapidly in the later 

 part of the plant's life. A much smaller amount of phosphoric acid 

 than of nitrogen is absorbed from the soil, especially in the early 

 period of growth, as shown in the following table; 



