THE NlTKOGfiXOUS rRINOIPLES OF UKlNK 290 



The relative gain by growth, that o^ Xo. 1 assumed as 

 unity, is for No. 1 , — 1 



" " 2, — 61 

 " " 3^ _ 29 

 " " 4, — 28 



The crops were small, principally because the supply 

 ofunitrogen was very limited. 



These experiments demonstrate that the substances 

 added, in every case, aided growth by supplying nitro- 

 gen. They do not, indeed, prove that the organic fertil- 

 izers entered as such into the crop without decomposition, 

 but if urea escapes decomposition in a soil, as Cameron 

 and Cloez have shown is true, it is not to be anticipated 

 that the bodies employed in these trials should suffer al- 

 teration to ammonia-salts or nitrates. 



Hampe afterwards experimented with urea and uric 

 acid by the method of Water-Culture ( Vs. St., VII., 308 ; 

 VIII., 225 ; IX., 49 ; and X., 175). He succeeded in pro- 

 ducing, by help of urea, maize plants as large as those 

 growing in garden soil, and fully confirmed Cameron's 

 conclusion regarding the assimilability of this substance. 

 Hampe demonstrated that urea entered as such into the 

 plant. In fact, he separated it, in the pure state, from 

 the stems and leaves of the maize which had been pro- 

 duced with its aid. 



Hampe's experiments with uric acid in solution showed 

 that this body supplied nitrogen without first assuming 

 the form of ammonia-salts, but it suffered partially if not 

 entirely a decomposition, the nature of which was not 

 determined. Uric acid itself could not be found in the 

 crop. 



Hampe's results with hippuric acid were to the effect 

 that this substance furnishes nitrogen without reversion 

 to ammonia, but is resolved into' other bodies, probably 

 benzoic acid and glycocoll, which are formed when hip- 



