47 
QUESTION OF THE SOUECES OF THE NITROGEN OF VEGETATION. 
the amount of atmospheric ammonia absorbed by sulphuric acid, and the amount of 
combined nitrogen in the rain; and finally the amount of combined nitrogen in the 
drainage waters. 
The following is a summary of the amounts of nitrogen involved (in grams);— 
Initial—In soil 54'09, in rain 0’053, in ammonia of air 0'048, 
in plants 0‘35, total.= 54'541 
Final—In soil 56‘54, in drainage 0’403, in plants 2‘235, total . = 59d78 
Gain.= 4'63 7 
M. Berthelot points out that the gain of nitrogen is nearly equally divided between 
the soil and the plant, the latter having taken it up from the soil, which he considers 
is the true source of the gain. He compares the results with those formerly obtained 
without vegetation thus— 
Gains with vegetation.4‘64 and 7'58 grams. 
Gains without vegetation.12’70 and 23T5 grams. 
He assumes that there is with the higher plants, as with animals, a constant loss of 
nitrogen. He admits however that more evidence is needed absolutely to demonstrate 
that the plants themselves do not fix, and that they do set free, nitrogen. But he 
considers it proved by his experiments that vegetable soil does fix free nitrogen ; and 
he thinks it probable that this is the chief source of the gain by the higher plants. 
Thus, it can be understood how concentrated production exhausts faster than the 
natural actions restore fertility; whilst in natural vegetation, on the other hand, the 
fixing of nitrogen may exceed the liberation, and accumulation may thus take place, 
Beviewing the whole of these results and conclusions of M. Berthelot, it is in the 
first place to be observed that whilst the results obtained under the influence of the 
silent discharge in bringing nitrogen into combination with certain vegetable principles, 
owed their special interest to the inference that thus free nitrogen might be brought 
into combination within the plant, he now considers it at least doubtful, whether the 
higher plants do bring free nitrogen into combination at all, and that probably the 
gain of nitrogen is by the soil, and not by the plant. 
Obviously, if there are organic compounds existing within the soil which have the 
power of bringing free nitrogen into combination under the influence of electricity of 
feeble tension, such as occurs in the atmosphere, the soil and not the plant may be the 
source, and yet the agent be the feeble electric current. So far, however, as it is 
assumed that nitrogen is so brought into combination in the atmosphere itself, the 
resulting compound or compounds will be found in the air, and in the aqueous deposi¬ 
tions from it; and the extent, or rather the limit, of the amount of combined nitrogen 
so available over a given area, in Europe at any rate, is pretty well known. 
