The Atmosphere as a source of Nitrogen to Plants. 
257 
water. The proportion of nitrogen contained in them having 
been carefully ascertained by analysis of a similar quantity of the 
same seed, it only remained to ascertain the quantity of this ele- 
ment present in the crop. If the ammonia in the air supplied 
was sufficient to account for the excess of nitrogen in the crop 
over that in the seed, we might be justified in concluding that 
this ammonia was the source of the increase. If, on the other 
hand, the gain in nitrogen was more than could be ascribed to the 
ammonia, we should be forced to acknowledge that some other 
source of nitrogen, probably the atmospheric nitrogen, had inter- 
vened. So reasoned M. Ville. I should add that he supplied 
to the plants a small quantity of carbonic acid gas, which he found 
was very necessary to their well-being. The plants operated 
upon were cress, lupins, rape, wheat, rye, and Indian corn ; the 
result of these experiments was, that the crops in most cases con- 
tained considerably more nitrogen than that present in their 
seeds, and (as ammonia) in the air supplied to them. 
M. Ville came to the conclusion that plants assimilate the 
atmospheric nitrogen. In a subsequent series of experiments 
made to check the above, M. Ville took measures to deprive the 
air, before entering the cases, of all the ammonia which it con- 
tained, so that any gain in nitrogen of the produce over that in 
the seeds could not be traced to the agency of ammonia. The 
result was the same as before — the gain of nitrogen was un- 
doubted, and his first conclusions were abundantly confirmed. 
Judging from the account which he himself has given of the 
methods employed, we cannot sufficiently praise the great intelli- 
gence and exactitude brought to bear upon these experiments. 
It is impossible to detect any source of error, and the results 
would seem to be in every respect trustworthy ; but are we pre- 
pared to admit M. Ville's conclusions, that atmospheric nitrogen 
can be assimilated by plants ? This is a question which we shall 
presently consider. 
In a third set of experiments M. Ville shows the effect upon 
plants of an increased supply of ammonia in the air in which they 
grow. The plants selected were rape, wheat, rye, Indian corn, 
tobacco, &c. They were sown as before in sand, and supplied 
with water and plenty of fresh air daily. To the air of one 
case the vapour of ammonia was added. The results were most 
marked ; not only was the amount of crops growing in the ammo- 
niacal air increased, but the relative per centage proportion of 
nitrogen in it was largely augmented. M. Ville, therefore, 
although believing in the power of plants to absorb atmospheric 
nitrogen, does not for an instant question the great influence of 
ammonia on vegetation. On the contrary, he suggests the arti- 
ficial employment of the volatile carbonate of ammonia in the air 
VOL. XVI. s 
