1905.] Function of Silica in the Nutrition of Cereals. 467 



In tig. 6 curves are seen representing the same succession of plots, this 

 time however they all receive potassic manure. Again, the proportion of 

 grain on the plot without either phosphoric acid or silica, 3, is low, ami 

 its formation is retarded as compared with the normal. Plots 4 and 4 S, 

 the two plots receiving phosphoric acid, are practically identical and agree 

 closely with the normal, while the curve representing Plot 3 S, where silica 

 but no phosphoric acid is used, occupies an intermediate position. The 

 development of grain on these plots receiving potash is later than is 

 normal, though ultimately as high a proportion of grain to straw is 

 produced. 



As regards the formation of grain, the curves show that phosphoric acid 

 hastens the formation of grain, and eventually causes a higher proportion of 

 the material in the plant to pass over into that state, while silica acts in the 

 same direction, though not to so large an extent. 



Juneis 20 27 July 4 11 18 25 Aug 1 8 



Fig. 7. — Percentages of Nitrogen in Dry Matter. 



Turning to the entry of the nitrogen, fig. 7 shows the percentage of 

 nitrogen in the grain and straw at the successive dates and for the four plots 

 receiving no potash, the mean results being also plotted for purposes of 

 comparison. Plot 1, receiving neither phosphoric acid nor silica, yields the 

 highest proportion of nitrogen in both grain and straw at each stage of the 



