204 The Development of the Grain of Wheat 



Plot 10. 



July 1 G— August 3 1 -098 



August 3— 21 1-868 



Red Fife, 1907. 



July 25— August 12 rG02 



August 12— 30 24.52 



Square Head's Master, 1908. 



July 8—21 1-552 



July 21— August 8 1-912 



These figures show that the material filled into the grain is more 

 nitrogenous in the later than in the earlier stages. 



A better idea of what takes place may be obtained by dividing the 

 whole period into three stages suggested by the variations in the water 

 in the grain. 



In the first stage the larger part of the grain consists of the soft 

 tissue forming the pericarp, the subsequent shrinkage of which into dry 

 membranes is practically complete by the end of the first stage. The 

 endosperm exists during all the first stage and at the end is beginning 

 to show starch, &c. throughout. The material forming the pericarp 

 evidently contains more nitrogen than that which enters the endo- 

 sperm later. The middle stage is characterised by the filling in of the 

 endosperm, and in the last stage the migration is coming to an end ; 

 during this period the material that is stored appears to be more 

 nitrogenous because the entry is slow, while the losses by respiration, 

 which fall wholly on the non-nitrogenous substance, are still going on. 



Ash and PJiosphoric Acid. The proportion of ash in dry matter, 

 and the amounts of ash and of phosphoric acid in 1000 grains, yield 

 curves exactly similar to those given by nitrogen, indicating that the ash 

 and the phosphoric acid enter the grain pari passu with the nitrogen. 

 Table I. shows the ratio of phosphoric acid to nitrogen for each sample, 

 and indicates that the wheat on each plot manufactures material 

 possessing a composition special to itself, but one which remains 



