1905.] Function of Silica in the Nutrition of Cereals. 461 



of the crop need only be investigated, i.e., the period during which the 

 nutrition of the plant from the soil has largely ceased and assimilation is 

 coming to a standstill, while the materials previously accumulated in the 

 stem and leaf are migrating into the seed. 



The method adopted was to take a certain number of rows of barley in the 

 middle of each plot and remove the whole plant, as far as possible with the 

 roots intact, for two yards up these rows, at weekly intervals from June 13 

 until harvest on August 8, or nine times in all. The plants were then air- 

 dried after washing the roots free from soil, the grain when formed was 

 separated from the straw, and both were finally dried in the steam oven, so 

 as to obtain the weight of dry matter ; although dealing with such small areas 

 it. is impossible to make more than a very approximate estimate of the yield 

 per unit area. The dried material was ground, and after determinations of 

 the nitrogen in one portion, the rest was burnt for ash, in which the pure 

 ash, free from sand and charcoal, and the phosphoric acid and silica were 

 determined. 



The analytical results are set out in Appendix Tables VII to X, from 

 which are derived the various curves of development now to be considered 

 (figs. 1 to 11). Before however proceeding to a consideration of particular 

 cases it will be convenient to trace by means of an average result for all the 

 plots the general course of development in the later stages of the growth of 

 the barley plant. 



Grams 



300 



200 



















• Actual 

 Smoothed 

















V ' 





















Actual 

 Smoothed 









June 13 20 27 July 4 n 18. 25 Awg.i 8 



Fig. 1. — Dry Weights. Mean of all plots. Whole Plant and Grain. 



Fig. 1 shows the mean dry weight of all the eight plots on each date, both 

 of the whole plant and of the grain. The crop attained its maximum weight 

 about July 18 — 25, after which it remained stationary and probably indeed 

 declined slightly. The result shown for August 1 is clearly exceptional ; on 



