QUESTION OF THE SOURCES OF THE NITROGEN OF VEGETA^J’ION. ‘->0 
a loss of 15 per cent, of nitrogen, and the still greater gains if there had been a loss 
of 45 per cent., as in an experiment by Boussingault under special conditions. 
Further, he says that whilst actually observed gains are proof of the acquisition of 
nitrogen, the failure to show gain only proves non-fixation, if it he proved that there 
was no liberation. He suggests that the negative results obtained by Boussingault 
and at Bothainsted may be accounted for by liberation ; though at the same time he 
recognises that the conditions of the experiments excluded the action of either 
electricity or microbes. We may remark that, in the experiments both of Boussin¬ 
gault and at Bothamsted, any cases of decay were carefully observed, and the losses 
found explained accordingly; and it may be confidently asserted that the conclusions 
drawn were not vitiated by any such loss. This specious objection, putting out of 
court all negative results, is, however, a very old one; as also is the one resuscitated 
by Atwater, that luxuriance must be forced to a certain degree to favour the fixation 
of free nitrogen. On this point we may state that the results obtained at Bothamsted 
were as distinctly negative when luxuriance was favoured by supplies of combined 
nitrogen as when it was not. 
Atwater concludes that his results do not settle whether the nitrogen gained was 
acquired as free or combined nitrogen, by the foliage, or by the soil. He considers, 
however, that, in his experiments, the conditions were not favourable for the action 
either of electricity or of micro-organisms; and he favours the assumption that the 
plants themselves were the agents. Lastly, he considers the fact of the acquisition of 
free nitrogen in some way to be well established; and that thus facts of vegetable 
production are explained, which otherwise remain unexplained. To this, and other 
points involved, we shall refer again in our concluding remarks. 
Lastly, we have to summarise those of the results and conclusions of Boussingault 
which bear upon the present aspect of the question of the sources of the nitrogen of 
vegetation. In his earlier experiments, as in those at Bothamsted, sterilised materials 
had been used as soils ; but in 1858 he commenced a series in which more or less of a 
rich garden soil was mixed with sand and quartz. In some cases the plants were 
grown in free air, and rn others in closed vessels with confined air. In several cases 
there was more or less gain of nitrogen; but the greatest gain was in an experiment 
with a lupin grown in a closed vessel. Boussingault points out that it was the soil 
and not the plant that had fixed the nitrogen. The result was so marked that he 
repeated the experiment in 1859, when he obtained almost identically the same amount 
of gain as in 1858. He also put 120 grams of the rich soil into a shallow dish, 
moistened it with distilled water, and exposed it to the air as an experiment on fallow. 
The results showed a small gain of nitrogen. 
Boussingault further found that mycodermic vegetation went on in rich soil, and 
he considered the gains of organic nitrogen represented the remains of such vegeta¬ 
tion ; whilst the fallow experiment indicated that the experimental plants had little 
to do with the action. His general conclusion was, that from the numerical results 
