QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETATION. 
87 
In regard to these new results Boussinoault says that, contrary to his anticipation, 
the combustion of the carbon of the non-nitrogenous organic matter, the cellulose, 
added to the soil, had not favoured the production of nitric acid. 
He gives reasons for concluding that the process of nitrification had been completed 
before the opening of the vessels in 1871. At the same time, he shows that the 
amount, both of oxygen, and of salifiable bases, remaining, was sufficient for the 
production of much more nitrate. 
Upon the whole he concludes as follows :— 
It results from these researches, that, in the nitrification of vegetable soil, in a 
confined atmosphere not renewed, that is in stagnant air, gaseous nitrogen does not 
appear to contribute to the formation of nitric acid. The nitrogen determined in the 
soil in 1871, was not more than, but was even not quite so much as, in 1860. In the 
conditions of the experiment, the nitrification must have taken place at the expense 
of the organic substance of humus, which is found in all fertile soils. 
Although, as we have already said, the experiments in question were obviously 
suggested by the results obtained in 1858 and 1859, which showed a gain of nitrogen, 
Boussingault does not, throughout the discussion of the new results, offer any 
explanation of, or even refer to, the earlier ones. Further, it will be observed that in 
recording the negative results of the new experiments, he is careful to define the 
conditions under which they were obtained. 
Always placing the greatest reliance, both in the work and in the conclusions of 
Boussingault, we had been much impressed with the significance and importance 
of the earlier results and conclusions above referred to, whicn did not seem to be 
satisfactorily explained by the new ones, and in April, 1876, one of us wrote to him 
as follows :— 
“We have been very much struck with some of your results with Leguminosse, 
especially those with lupins in confined air in 1858 and 1859, and those with lupins 
and haricots in free air in 1858. May I ask whether it is your opinion that the free 
azote of the air does enter into combination, either by the direct agency of 
vegetation, or through that of the soil % And, if so, under what conditions do you 
think this action takes place, and what is the nature of the action ? ” 
In answer Bqussingault wrote a long and interesting letter, dated May 19, 
1876, in which he discussed various points of the subject of the sources of the nitrogen 
of vegetation, and replied as follows in reference to the special questions relating to 
his experiments in 1858 and 1859 :— 
“ Quant a I’absorption de I’azote gazeux de fair par la terre vegetale je ne connais 
pas une seule observation irreprochable qui I’etablisse ; non seulement la terre n’absorbe 
pas d’azote gazeux mais elle en emet, ainsi que vous favez reconnu avec j\Ir. Lawes, 
comme la vu Reiset pour le fumier, comme nous I’avons constatd, M. Schlcesing et 
moi, dans nos recherches sur la nitrification. 
