58 HOW CROPS FEED. 
tural plants to the production of the albuminoids.* We 
measure the nutritive effect of ammonia salts applied as 
fertilizers by the amount of nitrogen which vegetation as- 
similates from them. 
Effects of Ammonia on Vegetation, — The remarkable 
effect of carbonate of ammonia upon vegetation is well’ 
described by Ville. We know that most plants at a cer- 
tain period of growth under ordinary circumstances cease 
to produce new branches and foliage, or to expand those 
already formed, and begin a new phase of development in 
providing for the perpetuation of the species by producing 
flowers and fruit. If, however, such plants are exposed 
to as much carbonate of ammonia gas as they are capable 
of enduring, at the time when flowers are beginning to 
form, these are often totally checked, and the activity of 
growth is transferred to stems and leaves, which assume 
anew vigor and multiply with extraordinary luxuriance. 
If flowers are formed, they are sterile, and yield no seed. 
Another noticeable effect of ammonia—one, however, 
which it shares with other substances—is its power of deep- 
ening the color of the foliage of plants, This is an indi- 
cation of increased vegetative activity and health, as a 
pale or yellow tint belongs to a sickly or ill-fed growth. 
A third result is that not only the mass of vegetation 
is increased, but the relative proportion of nitrogen init is 
heightened. This result was obtained in the experiment of 
Peters and Sachs just described. To adduce a single other 
instance, Ville found that grains of wheat, grown in pure 
air, contained 2.09 per cent of nitrogen, while those which 
were produced under the influence of ammonia contained 
3.40 per cent. 
* In tobacco, to th2 production of nicotine ; in coffee, of caffeine; and in many 
other plants to analogous substances. Plants appear oftentimes to contain 
small quantities of ammonia salts and nitrates, as well as of asparagin, (C4 Hg 
Ne O3g,) a substance first found in asparagus, and which is formed in many 
“plants when they vegetate in exclusion of light, 
