516 MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
gen of the decomposing nitrogenous body. Or, if it did act upon the latter in preference 
to the former, there would either be no free Nitrogen finally evolved, or, in case of Ni- 
trogen being lost in the free state, it would be obvious that there had been less nascent 
Nitrogen converted into ammonia than had been liberated from its combinations, and 
hence that, as a resultant, there would be a loss and not a gain of combined Nitrogen 
due to the decomposition. 
The fact that, in our experiments upon the gas evolved by vegetable matters in a state 
of decomposition, both free Nitrogen and free hydrogen were given off, bears strongly 
upon this question. The Nitrogen evolved has been in most intimate contact with the 
hydrogen given off. It has, indeed, been in the identical cells by the decomposition of 
the walls or contents of which the hydrogen was set free; yet both appear as gas. 
From the above considerations it would appear that we need be under little appre- 
hension of error in the results of our experiments on the question of the assimilation 
of free Nitrogen by plants, arising from an unaccounted supply of ammonia formed under 
the influence of nascent hydrogen, given off in any decomposition of the organic matter 
involved in the experiment. 
Summary Statement of the Results of the foregoing consideration of the conditions required, 
or involved, in Experiments on the question of the assimilation of free Nitrogen by 
Plants. 
Before entering upon the discussion of the results of our direct experiments upon the 
question whether or not plants assimilate free Nitrogen, it will be well, for the sake of 
perspicuity, to give a very brief enumeration of the results arrived at in the foregoing 
Sections I. and II. (Part II.), relating to the conditions of experiment required, and to 
the collateral investigations involved, in the inquiry. They may be stated as follow :— 
1. Conditions of soil or matrix which are both adapted for healthy growth and are 
consistent with the other requirements of the investigation can be attained (Section I. 
Sub-sections A, p. 470, and L, p. 484). 
2. The requirements of the experiment in regard to the selection of seeds or plants 
for growth, to the nutriment to be supplied in the soil, to the water, to the atmosphere, 
to the carbonic acid, and to other conditions involved, can be satisfactorily met (Sec- 
tion I. Sub-sections B—J, inclusive, pp. 472-481; and L, p. 484). 
3. The conditions of experiment adopted have several advantages over some of those 
which have been suggested, or adopted, by others (Section I. Sub-section K, pp. 481- 
483). 
4, The mutual actions of the soil, air, organic matter in the soil or in the plant, are 
not such as to be likely to affect the result of the experiment, by yielding to the plants 
a quantity of combined Nitrogen not taken into account. The influence of Ozone as a 
possible element in these actions would be less, in the circumstances of the experiments 
