QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETATION. 
83 
explains, facts of vegetable production otherwise unexplained; and the fact of its 
acquisition in considerable quantities seems well established. 
We have pointed out that in Berthelot’s later papers he seems to rely much more 
on the agency of micro-organisms, than on that of electricity, in explanation of the 
phenomena of the fixation of free nitrogen; whilst Atwater does not consider that 
the conditions of his own experiments are favourable to the supposition that either 
of these agencies was the cause of the fixation which his results show. 
It need only be added, that the assumption that the real gains are generally greater 
than the experimental results indicate, on account of the losses that have taken place, 
is a very old one, it having been brought against the negative results obtained by 
Boussingault, and at Bothamsted, thirty or more years ago. It is still, however, as 
has been seen, a favourite argument with others as well as Professor Atwater. We 
have already said, that neither the conclusions of Boussingault, nor those drawn 
from the Bothamsted experiments, were vitiated by virtue of such loss. Further, 
the supposition that the assimilation of free nitrogen is the greater when luxuriance 
is favoured to a certain degree by artificial supplies of combined nitrogen, owes its 
origin to about the same date. The result was, however, as distinctly negative in the 
experiments at Bothamsted when luxuriance was so favoured, as when it was not. It 
is freely admitted, however, that in many of the experiments of Boussingault, as in 
those at Bothamsted, the arrangements were such as to exclude the agency, either of 
electricity or of micro-organisms. To this point we shall refer again presently. 
9. Recent results and conclusions of M. Boussingault. 
We have frequently discussed the results of M. Boussingault, obtained from 1837 
to 1854, and expressed entire agreement with the conclusions he drew from them 
under the conditions provided ; and it is not the object of the present comments to 
reconsider them in any detail. The question of the fixation of free nitrogen has, 
however, assumed a new aspect in recent years. It is now supposed that fixation, 
either by the plant, or within the soil, takes place, if at all, by the agency of 
electricity, or of micra-organ isms, or of both; and there can be no doubt, that the 
earlier vegetation experiments of Boussingault above referred to, as well as those 
conducted at Bothamsted about thirty years ago, were so arranged as to exclude the 
influence of either of those agencies. If, therefore, it should be established, that 
fixation does take place under their influence, and that such influence is essential for 
the development of the action, the conclusions, both of Boussingault and ourselves, 
from the results in question, are so far vitiated. It is to some of Boussingault’s 
more recent results, which have a bearing on this new aspect of the question, that we 
propose now to refer. 
In Boussingault’s previous vegetation experiments he had used sterilised materials 
as soils. But, in 1858,'^'' he commenced a series in which he employed more or less of a 
* ‘ Coniptes Rendus,’ vol. 48, 1859, p. .303. ‘ Agrononiie, Ac.,’ 2'^ edit., vol. 1, I860, p. 283. 
