1905.] Function of Silica in the Nutrition of Cereals. 465 



trace the effect of silica on the assimilation of carbon (dry matter yield), 

 nitrogen, and phosphoric acid, and particularly on the movement of these 

 materials into the grain. Figs. 3 and 4 show in graphic form the yield from 

 individual plots, fig. 3 deals only with Plots 1 and 2, where no potash is 

 supplied in the manure, while fig. 4 deals witli Plots 3 and 4, each of which 

 receives equal amounts of sulphates of potassium, sodium and magnesium. 

 In each figure curves are drawn separately for the silicated and non-silicated 

 portions of the plot. 



The accidental fluctuations in yield from week to week are too violent to 

 admit of smoothing, but the general character of the curves shows that 

 Plots 1 and 3, which receive neither phosphoric acid nor silica, give con- 

 sistently a much lower yield than the others. The curves representing 

 Plot 2 (with phosphoric acid), Plot 1 S (with silica), and Plot 2 S (with both 

 phosphoric acid and silica), do not differ from one another by more than the 

 extent of the accidental fluctuations from week to week of any one of them, 

 but all indicate a yield about half as large again as that of Plot 1. Similarly 

 where potash is used : Plot 3, without silica or phosphoric acid, never yields 

 much more than half the crop on the Plots 3 S, 4, and 4 S, receiving either 

 silica or phosphoric acid, or both together. As judged then by the dry 

 matter produced, the silicate manuring is able to do the same work for the 

 plant as the phosphatie manuring on Plots 3 and 4. 



Despite the magnitude of the accidental fluctuations some differences in 

 the character of the curves may be discerned ; both Plots 1 and 3 (without 

 silica or phosphoric aqid) reach their maximum only on August 8, whereas in 

 five of the other six cases where silica and phosphoric acid form part 

 of the manure the maximum is reached by July 18 or 25. This would 

 confirm the appearance in the field of deferred maturity in the absence 

 of either phosphoric acid or silica. 



Fig. 5 shows the proportion the grain bears to the whole plant at weekly 

 intervals for the four plots which receive no potash, together with the 

 smoothed mean of all the plots for comparison. It will at once be seen that 

 on Plot 1, receiving neither phosphoric acid nor silica, the proportion of 

 grain is below the normal, and also that the grain is later in forming. The 

 3 per cent, or so indicated on July 4, the earliest date when any separation 

 of grain was possible, would be wholly made up of the adherent pales. It 

 is only in the following week that the weight of grain has become sensible on 

 Plot 1. On Plot 2, receiving phosphoric acid, the formation of grain precedes, 

 and also is finally somewhat above the normal. 



Plot 1 S, receiving silica but not phosphoric acid, occupies an intermediate 

 position ; though starting a little later than Plot 2, it eventually becomes 



