512 MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
site apparatus sufficiently air-tight, was not followed up to the extent which had been 
intended. 
The plan proposed was, to place the organic matter in an atmosphere of pure oxygen, 
and to afford a constant supply of the gas as it became converted into carbonic acid, and 
was absorbed by a solution of caustic potash. 
The results obtained go to show that, in the presence of free oxygen, Nitrogen gas is 
evolved. But as the investigation is as yet so incomplete, owing to the circumstance 
above alluded to, we prefer not to give the results until we can confirm them by a more 
extended series of experiments under more favourable conditions. 
Taking together the results of all the experiments which have been made upon the 
decomposition of nitrogenous organic matters, they obviously point to a serious difficulty 
in the way of experiments made upon the question of the assimilation of free Nitrogen 
by plants. It is not possible to conduct any such experiments without exposing nitro- 
genous organic matter to conditions more or less analogous to those under which the 
loss of Nitrogen recorded in Tables VII. and IX. took place. For although, as Bous- 
SINGAULT has shown, there may be no loss of Nitrogen during germination, yet, during 
the entire period of the growth of a plant, certain portions of the vegetable substance 
may be subjected to conditions favourable to the decomposition of its nitrogenous com- 
pounds, and to the evolution of free Nitrogen. 
As illustrative of how far these conditions are likely to be operative in the manner 
indicated, the following results, made with Wheat, Barley, and Oats respectively, are 
very instructive. Seeds of the three plants were sown, each in precisely the same 
kind and amount of soil, &c., as employed in the experiments on the assimilation 
question. The three pots were placed beneath a large glass shade, 16 inches in diameter, 
which fitted into the groove of a stone-ware lute-vessel, into which sulphuric acid was 
poured to exclude the access of external air. The whole stood ona table in the diffused 
light of the laboratory. The plants were at first supplied with distilled water; but 
with no carbonic acid beyond that which might be contained in the water. These con- 
ditions afforded all that was necessary for germination and growth, with little oppor- 
tunity for the assimilation of free Nitrogen, even were this possible in the more favour- 
able conditions of sunlight. Yet the conditions were more than ordinarily favourable 
to the decomposition of nitrogenous compounds, provided this would take place, under 
certain circumstances, during the growth of the plant. The succulent character of the 
stems and leaves so grown in the shade, would render the nitrogenous matters more 
liable to decomposition than in the case of the more firm and hardened stems of piants 
grown in sunlight. 
Eight seeds of each plant were sown; and in a few days all came up, and grew very 
rapidly in height, without much tendency to development and expansion of leaf. The 
plants were all very much alike—tall, slender, delicate, and having the peculiar pale- 
green colour common to plants deprived of sufficient sunlight. In several other expe- 
