538 MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
tional supply of combined Nitrogen would cause increased development, so long must 
the physiological conditions have been such as to require available Nitrogen, and they 
must therefore have been more or less favourable to the assimilation of free Nitrogen, 
provided such assimilation were possible. Hence, the fact that this did not take place 
under the circumstances which have been described, seems to show that, at least in the 
case of these Graminacee, it is not possible. 
Some of the remarks which we have made with regard to the influence of a supply of 
combined Nitrogen upon the growth of the Graminacee, apply also, in a greater or 
less degree, to the other plants experimented upon. We shall not comment here in 
detail upon the value of each experiment, but simply call attention to the columns of 
gain or loss of Nitrogen, in the Tables, and to the notes in the Appendix indicating the 
circumstances of growth of the plants. 
With regard to the Leguminose experimented upon, it is to be observed that the 
development was by no means so satisfactory as in the case of the Graminacese. Hence 
the evidence which the results relating to them afford against the fact of assimilation 
of free Nitrogen must be admitted to apply to a more limited range of conditions of 
growth, and, therefore, to be less conclusive against the possibility of such assimila- 
tion. Still, so far as they go, the results with these plants, and also those with buck- 
wheat, tend to confirm those obtained under the more favourable circumstances of 
growth with the cereals. It will be remembered, however, that M. BoussInGAaULT expe- 
rimented with a great many Leguminous plants, and generally succeeded in getting 
much more healthy growth than we were able to do in the cases to which the figures in 
the Tables refer. Yet in no case did he find any such gain of Nitrogen as to lead him 
to the conclusion that these plants, any more than the Graminacee, assimilated free or 
uncombined Nitrogen. Our own experiments with Leguminous plants are, however, 
not yet concluded; so that we hope to supply some additional evidence on this subject, 
on a future occasion. 
Relations of the Plants grown with a supply of ammonia to those grown without it. 
We have already called attention to the fact that the physiological phenomena exhi- 
bited in the progress of the plants grown under the two different conditions as regards 
the supply of combined Nitrogen at their disposal, afford satisfactory evidence that the 
conditions provided in soil and atmosphere were all that were requisite in experiments 
for the solution of the question at issue with regard to the Cereals. The great develop- 
ment of these plants when ammonia was supplied (which was in fact almost in pro- 
portion to the amount supplied), the cessation of growth with the limit of the supply, 
together with the contrast between the growth with the aid of the ammonia and that 
without it, all afford evidence in one direction in regard to the question at issue, so far 
as these plants are concerned. 
In Table XIV., relating to the plants to which ammonia was supplied, an experiment 
with clover is recorded. Reference to the remarks in the Appendix, p. 073, will show 
