538 MB. J. B. LAWKS, DE. GHLBEBT, AND UK. PTJGH 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 tt 

 must therefore have been more or less favourable to the assimilation of tree 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 hast iu the 

 case of these Graminacea?, it is not possihle. 



Some of the remarks which we have made with regard to the influence of a supply of 

 combined Nitrogen upon the growth of the Graminaceae, 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 Leguminosae experimented upon, it is to be observed that the 

 development was by no means so satisfactory as in the case of the Graminaceae. 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. Boussixgault 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 Graminacea?, 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 groam 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. Eeference to the remarks in the Appendix, p. 573, will show 



