553 



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 that is subjected merely to the ex- 

 haustion required to supply materials for growth in the ordinary 

 process of germination. 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 objec- 

 tion to the application of nitrogenous organic manure in such expe- 

 riments. 



Although there can be no doubt of the evolution of hydrogen 

 during the decomposition of organic matter, and although it has long 

 been admitted that nascent hydrogen may, under certain circum- 

 stances, combine with gaseous nitrogen and form ammonia ; never- 

 theless, 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 de- 

 composition of the organic matter involved. 



The Authors next consider the questions, whether assimilation of 

 free nitrogen 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 

 when an excess of combined nitrogen is 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 



