557 



menters on the question whether plants assimilate free or uncom- 

 bined nitrogen, are very conflicting. 



The conditions provided in the experiments of the Authors on this 

 question were found to be quite consistent with the healthy develop- 

 ment of various Graminaceous Plants, but not so much so for that of 

 the Leguminous Plants experimented upon. 



It is not probable that, under the circumstances of the experiments 

 on assimilation, there would be any supply to the plants of an unac- 

 counted quantity of combined nitrogen, due to the influence either 

 of ozone or of nascent hydrogen. 



It is not probable that there would be a loss of any of the com- 

 bined nitrogen involved in an experiment on assimilation, due to the 

 evolution of free nitrogen in the decomposition of organic matter, 

 excepting in certain cases when it might be presupposed. 



It is not probable that there would be any loss due to the evolu- 

 tion of free nitrogen from the nitrogenous constituents of the plants 

 during growth. 



In numerous experiments with graminaceous plants, under a wide 

 range of conditions of growth, in no case was there any evidence of 

 an assimilation of free nitrogen. 



In experiments with leguminous plants the growth was less satis- 

 factory, and the range of conditions was, therefore, more limited. 

 But the results with these plants, so far as they go, do not indicate 

 any assimilation of free nitrogen. It is desirable that the evidence 

 of further experiments with such plants, under conditions of more 

 healthy growth, should be obtained. 



Results obtained with some other plants, are in the same sense as 

 those with graminaceous and leguminous ones, in regard to the 

 question of the assimilation of free nitrogen. 



Seeing the evidence afforded of the non-assimilation of free nitro- 

 gen by plants, it is very desirable that the several actual or possible 

 sources whence they may derive combined nitrogen should be more 

 fully investigated, both qualitatively and quantitatively. 



If it be established that plants do not assimilate free or uncom- 

 bined nitrogen, the source of the large amount of combined nitrogen 

 known to exist on the surface of the globe, and in the atmosphere, 

 still awaits a satisfactory explanation. 



