470 



Messrs. A. D. Hall and C. G. T. Morison. [Dec. 22, 



phosphoric acid which the plant had thus been able to acquire is moved off 

 into the grain. This may be seen more clearly in fig. 10, which shows what 

 proportion of the plant's phosphoric acid is to be found in the grain on the 

 successive dates. On Plot 1, without phosphoric acid or silica, the move- 

 ment of phosphoric acid to the grain begins much later, but is ultimately 

 more complete than on the normal or on the plots receiving phosphoric acid. 

 With silica but no phosphoric acid (Plot 1 S) the migration of phosphoric 

 acid begins at an earlier date and the proportion transferred is much 

 increased, in spite of the fact that the actual amount of phosphoric acid in 

 the plant is also much greater than on the first plot. Exactly the same 

 conclusions are derived from an examination of the curves yielded by the 

 parallel plots receiving potash (fig. 11) ; the use of silica both accelerates the 

 migration of phosphoric acid to the grain and makes it more complete, 

 although a greater proportion is initially present. 



80%r 



6o% 



40% 



20% 











^ — Mean. 

































IS 



25 



Aug.I 



July 4 



Fig. 11.— Phophoric Acid. Percentage of whole content present in Grain. Plots 



with Potash. 



The fact that a greater proportion of the phosphoric acid present in the 

 plant is utilised in the grain on the silica plots, seems for the first time to 

 indicate some specific action of the silica in facilitating the migration of 

 phosphoric acid, so that it is not left unused as waste material in parts of 

 the plant no longer active. But it will be found that the actual percentage 

 of phosphoric acid finally left in the dry matter of the straw is no lower 

 where silica has been used, on Plots 1 S and 3 S, than on the corresponding- 

 Plots 1 and 3 without either phosphoric acid or silica. If something like 



