300 HOW CROPS FEED, 
puric acid is subjected to the action of strong acids or 
ferments. 
Hampe, therefore, experimented with glycocoll, and 
from his trials formed the opinion that this body is di- 
rectly nutritive. In fact, he obtained with it a crop equal 
to that yielded by ammonia-salts, 
Knop, who made, in 1857, an unsuccessful experiment 
with hippuric acid, found, in 1866, that glycocoll is as- 
similated (Chem. Centralblatt, 1866, p. 774). 
In 1868, Wagner experimented anew with hippuric 
acid and glycocoll. His results confirm those of Hampe. 
Wagener, however, deems it probable that hippuric acid 
enters the plant as such, and is decomposed within it into 
benzoic acid and glycocoll ( Vs. St., XI., p. 294). 
Wagner found, also, that kreatin is assimilated by 
vegetation. 
The grand result of these researches is, that the nitrog- 
enous (amide-like) acids and bases which are thrown off 
in the urinary excretions of animals need not revert, by 
decay or putrefaction, to inorganic bodies (ammonia or 
nitric acid), in order to nourish vegetation, but are either 
immediately, or after undergoing a slight and easy altera- 
tion, taken up and assimilated by growing plants. 
As a practical result, these facts show that it is not 
necessary that urine should be fermented before using it 
as a fertilizer, 
8 9. 
COMPARATIVE NUTRITIVE VALUE OF AMMONIA-SALTS AND 
NITRATES. 
The evidence that both ammonia and nitric acid are ca- 
pable of supplying nitrogen to plants has been set forth. 
It has been shown further that nitric acid alone can per- 
fectly satisfy the wants of vegetation as regards the ele- 
ment nitrogen. In respect to ammonia, the case has not 
Bx 
