Behaviour of Silicates. 167 



sulphuric acid, and silica the less, the greater the amount of 

 the ammonia- salts applied, and the coarser the herbage. 



The only noticeable difference between the two plots 11 in 

 the percentage mineral composition of the herbage is, that 

 there is a slightly higher percentage of silica in that of the 

 plot on which it was applied, and with this there is a less 

 percentage of potash, and a less increased percentage of it 

 over the later years. At the same time, there is a somewhat 

 less excessive percentage of nitrogen where the silicates were 

 used. In the presence of the excessive supply of nitrogen, 

 and the increased activity of growth induced by it, the 

 silicates of soda and lime employed were probably effective 

 in other ways than merely as supplies of either silica, or 

 soda, or lime, to the plant. The effect was probably due in 

 part to reactions of the alkaline silicates within the soil ; for, 

 under their influence, there was more nitrogen, magnesia, 

 potash, phosphoric acid, sulphuric acid, and chlorine, as well 

 as more silica, lime, and soda, taken up ; and, with these, 

 more carbon assimilated. 



Some useful facts may here be recalled. The dry matter 

 of the miscellaneous species generally contains a higher 

 percentage of mineral matter than that of the leguminous 

 herbage, and the leguminous a higher percentage than that 

 of the gramineous herbage; and the less matured the 

 produce, the higher, as a rule, will be the percentage of 

 mineral matter in its dry substance. Of the three, the ash of 

 the leguminous herbage contains the highest, and that of the 

 gramineous herbage the lowest percentage of lime, that of 

 the miscellaneous being intermediate. On the other hand, 

 the ash of the gramineous herbage is richest in potash, and 

 it will be the richer in potash, and the less rich in lime, the 

 greater the proportion of stem to leaf. 



10. 550Z&. Nitrate of Soda, with Mixed Mineral Manure 

 containing Potash-, Plot 14. The comparison in this case 

 (Table XL.) is with plot 9, which received mineral manures 

 along with nitrogen applied as ammonia-salts. The experi- 



