r»| I ME. .1. B. I,\\\i:s, DR GILBERT, AND DB, PI '.II OK 



very Limited distribution of the roots, and the foci thai no watei iva added do 

 growth, which would tend to distribute any soluble or otherv Ij transportable 



mailers, iirr conditions all consistent with the almost total absence of Nitrogen in the 

 soil. 



Lastly in regard to the results in the Table (XI.), the final column, showing the gain 



or loss of Nitrogen, affords us the means of judging how far the molecular actions by 

 which free Nitrogen was given off in the cases of the experiments upon the decom- 

 position of nitrogenous organic matter are likely to interfere with the results of our 

 investigations on i be question of assimilation of free Nitrogen by plants. It ;is seen that, 

 in the experiments now under consideration, no free .Nitrogen was given off during the 

 process of germination and growth. At least, the assumption that free Nitrogen was 

 given off implies the still more improbable one, that, under the circumstances detailed, 

 assimilation of free Nitrogen lias taken place; whilst the adoption of these two assump- 

 tions necessitates the yet more improbable one, that these two independent actions bear 

 a most definite relation to each other — in fact, that the amount of free Nitrogen 

 assimilated is exactly equal to that given off during decomposition. 



It would appear, therefore, that we may rest satisfied that our results in regard to the 

 question of assimilation will not be affected by a loss of free Nitrogen as the result of 

 the decomposition of nitrogenous organic matter, so long as that matter is subjected to 

 the ordinary process of germination, and exhaustion to supply materials for growth. 

 Our results in regard to the products of decomposition of nitrogenous organic matter do, 

 indeed, point to the danger of using nitrogenous organic manure in such experiments, and 

 to the error that might occur from seeds decomposing in the soil instead of growing, or 

 from the decomposition of dead leaves, of old roots, or of nitrogenous organic excretions ; 

 but they do not afford any evidence of what takes place within the range of the action 

 of the living plant. And, judging from the amount of free Nitrogen evolved when, as 

 in the experiments on decomposition, so large a proportion of the nitrogenous organic 

 matter was decomposed, we may form some idea of the probable extent of such evolu- 

 tion when, as in experiments where vegetable growth is involved, and where the only- 

 nitrogenous organic matter supplied is that in the seed sown, but a small proportion of 

 the total nitrogenous matter undergoes decomposition. 



In relation to this question, it should be borne in mind that, in the cases where the 

 large evolution of free Nitrogen took place, the organic substances were subjected to 

 decomposition for a period of about six months, during which time they lost three-fourths 

 of their carbon. In the experiments on the question of the assimilation of free Nitrogen, 

 however, but a very small proportion of the total organic matter is subjected to decom- 

 posing 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 little carbon is lost. It would appear, then, that we need not fear any 

 serious error in our experiments in regard to the latter question, arising from the 

 evolution of free Nitrogen in the decomposition of the nitrogenous organic matters 



