22 



found that very small qnantitics of nitrogen wcro so taken up ; but 

 both concluded that the action takes place in very immaterial degree 

 in natnral vegetation. 



We have elsewhere shown that a consideration of the chemistry 

 and the physics of the subject would lead to the conclusion that the 

 plants which assimila'^e more nitrofjfen over a given area than others 

 do not do so by virtue of a greater power of absorbing already com- 

 bined nitrogen from the atmosphere by their leaves. But, apart from 

 such considerations, our statistics of nitrogen production seem to pre- 

 elude the idea tliat the broad-leaved root-crops, turnips and the like, 

 to which the function has with the most confidence been attributed, 

 take up any material proportion of their nitrogen by their leaves from 

 combined nitrogen in the atmosphere. We need only here recall atten- 

 tion to the fact that the yield of nitrogen in these crops, even with 

 the aid of a complex mineral manure, was in the later years reduced 

 to as low a point as in the cas^ of the narrow-leaved cereals. 



:i 



Do Plants Assimilate Free Nitrogen? 



The question still remains to consider — whether plants assimilate 

 the free nitrogen of the atmo.sphero, and whether some descrijitions 

 do so in a much greatc ' degi'ee than others ? It is freely admitted 

 that if this were establisued many of our difficulties would vanish. 



This question has been the subject of a great deal of experimental 

 inquiry, since the time that Boussingault entered upon it about the 

 year 1837 ; and more than twenty years ago it was elaborately investi- 

 gated at Rothamsted. 



We will here give a snmmary of the very conflicting results which 

 have been published in reference to this subject, of the assimilation of 

 the free nitrogen of the atmosphere by plants, contining attention, for 

 want of space, to the three most comprehensive series of experiments 

 which have been undertaken relating to it. 



Though not the first in point of date, we will first refer to the 

 experiments of M. G. Ville, the results of which led him to conclude 

 that plants do assimilate the free nitrogen of the air — a view of 

 which he has been the arch-apostle for many years, and upon which 

 ho may be said to have founded a system, in his work on " Artificial 

 Manures." 



From 1849 to 1856, M. G. Ville made numerous experiments on 

 this subject. The following table (VI) gives a summary of his results, 

 and shows the special conditions of each separate series of experi- 

 ments: — 



