82 
SIR J. B. LAWES AND PROFESSOR J. H. GILBERT ON THE 
should be remarked, however, that Boussingault himself, after he had acquired much 
more experience, both in the conduct of vegetation experiments, and in analytical 
method, entirely disallowed that the results of those early experiments were evidence 
of the fixation of free nitrogen. He also quotes Boussingault’s later experiments ; 
made in 1851, 1853, and 1854, and says in regard to them that—“even the cereals, 
oats and wheat, contain 17 to 32 per cent, more than was supplied in the seed. The 
results differ from those of the previous series in that the cereals here show more, and 
the legumes less, gain of nitrogen.” Now, in the 6 cases with haricots and lupins 
referred to, the amounts of nitrogen supplied in the seed ranged from 19‘9 to 36’7 
rnillig., and they show, respectively—2'3 millig. actual loss, and 3’2, 2‘5, 4'2, 3'0 and 
2'0 millig. actual gain. In the case of the cereals, on the other hand, the total amount 
of nitrogen supplied in the seed was, with the oats only 3'1, and with the wheat only 
6‘4 millig., and the actual gains shown were only 1‘0 and I'l millig. Yet, 
Atwater shows that these last results, calculated into percentage, represent gains of 
32 and 17 per cent, of the original nitrogen, and larger gains even than with the 
legumes ! It need hardly he said, that Boussingault interpreted these later results 
as not indicating any fixation of nitrogen. 
Briefly summarised, Atwater’s conclusions are :— 
1. —That in some of his experiments with peas, half or more of the total nitrogen 
of the plants was acquired from the air. Where the gains were small, or there was 
a loss, the conditions were abnormal, and it is to be assumed that there was loss, 
either from the nitrate of the nutritive solutions, from the seeds during germination, 
or from the growing plants. 
2. —An actually observed gain is positive proof that nitrogen has been assimilated, 
either directly by the plants, or indirectly through the medium in which tire roots 
have developed. The failure of an experiment to show gain only proves non-assimila¬ 
tion, if it is also proved that there was no liberation of nitrogen. The conflicting 
results of various experimenters may probably be explained by the fact of such 
liberation. 
3. —The experiments do not show in what way the nitrogen is acquired. It must 
have been taken up, either as free or combined nitrogen, either directly through the 
foliage, or indirectly through the soil and nutritive solutions, and the roots. 
4. —It is possible that the negative results of Boussingault, and ourselves, are due 
to the liberation of free nitrogen. The conditions were, moreover, such as to exclude 
the action of electricity and of microbes. 
5. -—Since Berthelot has shown that nitrogen may be fixed in organic matter by 
the agency of electricity, and in soils by the agency of micro-organisms, some cases of 
gain may he so explained; but it is considered that the conditions for such actions did 
not exist in his own experiments. The balance of evidence favours the assumption 
that the plants themselves were the agents. 
6. —The conclusion that plants acquire atmospheric nitrogen accords with, and 
