528 | Royal Society :— 
question of assimilation, however, but a very small proportion of the 
total organic matter is submitted to decomposing actions apart from 
those associated with growth, and this for a comparatively short 
period of time, at the termination of which the organic form is 
retained, and therefore but very little carbon is lost. It would 
appear, then, that in experiments on assimilation no fear need be 
entertained of any serious error arising from the evolution of free 
nitrogen in the decomposition of the nitrogenous organic matter 
necessarily involved, so long as it is subjected to the ordinary 
process of germination, and exhaustion to supply materials for 
growth. On the other hand, the facts adduced afford a probable 
explanation of any small loss of nitrogen which may occur when 
seeds have not grown, or when leaves, or other dead matters, have 
suffered partial decomposition. They also point out an objection to 
the application of nitrogenous organic manure in such experiments. 
Although there can be no doubt of the evolution of hydrogen 
during the decomposition of organic matter under certain conditions, 
and although it has long been admitted that nascent hydrogen may, 
under certain circumstances, combine with gaseous nitrogen and form 
ammonia—nevertheless, from considerations stated at length in the 
paper, the Authors infer that there need be little apprehension of 
error in the results of their experiments, arising from an-unaccounted 
supply of ammonia, formed under the influence of nascent hydrogen 
given off in the decomposition of the organic matter involved. 
Turning to their direct experiments on the question of the assi- 
milation of free nitrogen, the Authors first consider whether such 
assimilation would be most likely to take place when the plant had 
no other supply of combined nitrogen than that contained in the 
seed sown, or when supplied with a limited amount of combined 
nitrogen, or with an excess of combined nitrogen? And again— 
whether at an early stage of growth, at the most active stage, or 
when the plant was approaching maturity? Combinations of these 
several circumstances might give a number of special conditions, in 
perhaps only one of which assimilation of free nitrogen might take 
place, in case it could in any. 
It is hardly to be supposed that free nitrogen would be assimilated 
if an excess of combined nitrogen were at the disposal of the plant. 
It is obvious, however, that a wide range of conditions would be ex- 
perimentally provided, if in some instances plants were supplied with 
no more combined nitrogen than that contained in the seed, in others 
brought to a given stage of growth by means of limited extraneous 
supplies of combined nitrogen, and in others supplied with combined 
nitrogen in a more liberal measure. It has been sought to provide 
these conditions in the experiments under consideration. 
In the selection of plants, it was sought to take such as would 
be adapted to the artificial conditions of temperature, moisture, &c. 
involved in the experiment, and also such as were of importance in 
an agricultural point of view—to have representatives, moreover, of 
the two great Natural Families, the Graminacee and the Legumiuose, 
