210 TJie Develoiwient of the Gram of Wheat 



proportioti of nitrogen and ash, though the percentage of phosphoric acid 

 in the ash is low. Both the dextrose and the diastatic power of the 

 grain are rising during this period. 



grama 

 ■06 



3 6 9 12 15 18 21 24 27 30 33 36 days 



Fig. 15. °/o protein nitrogen in total nitrogen, 1908 (upper curve). Actual 

 non-protein nitrogen in 1000 grains (lower curve). 



During the next period, which lasts about a month, the endosperm is 

 being filled up, and the dry Aveight of the grain is more than trebled, 

 but the actual amount of water present in the grain remains approxi- 

 mately constant. Throughout this time the material moved by the 

 plant and stored in the endosperm appears to be of constant composition, 

 as indicated by the uniformity of the N : PoOg : carbohydrate ratio of the 

 material entering between successive dates. Each wheat however 

 elaborates and stores a characteristic material, the composition of which 

 is determined beforehand by variety, soil (including manure), climate, 

 and similar factors independent of the migration process. The microscopic 

 examination of the grain would show that the cells of the endosperm are 

 filled progressively beginning from the base of the grain and proceeding 

 towards the tip, or end at which the embryo is developed, each set of 

 cells being successively filled up and then as it were put out of action. 

 The fact that the total amount of water, non-protein nitrogen, diastatic 

 power, and dextrose (though this latter material does not become constant 



