ON THE GROWTH OF LEGUMINOUS CROPS. 45 



nitrogen of the air, when drawn from the results of experiments in 

 which the plants were so enclosed as to exclude the possibility of 

 electrical action. More recently, he has objected to experiments so 

 conducted with sterilised materials, on the ground that, under such 

 conditions, the presence, development, and action, of micro-organisms, 

 are excluded. 



There is, however, I believe, nothing in the recent results, either of 

 Berthelot or of others, which can be held to invalidate the conclusion, 

 drawn from the results of Boussingault, and from those obtained at 

 Rothamsted about 30 years ago, that the higher plants do not fix 

 the free nitrogen of the atmosphere, under the conditions then adopted, 

 which, it is admitted, were such as to exclude, both electrical action, 

 and the influence of micro-organisms. 



I propose now to give a brief account of recently published 

 results and conclusions from experiments for the most part made 

 under such conditions as not to exclude the possibility of the 

 influence of electricity, or of micro-organisms. The first to notice are 

 those of M. Berthelot himself. 



M. Berthelot first showed that free nitrogen was fixed by various 

 organic compounds, under the influence of the silent electric discharge, 

 at the ordinary temperature; and he suggested that such actions 

 probably take place in the air during storms, and when the atmosphere 

 is charged with electricity, organic matters absorbing nitrogen and 

 oxygen. He also experimented with currents of much weaker tension, 

 more comparable with those incessantly occurring in the air, and in all 

 cases he found that nitrogen was fixed by the organic substance. The 

 gains were in amount such as would explain the source of the nitrogen 

 which he considers crops must derive from the atmosphere. 



Subsequently, he found that free nitrogen was brought into 

 combination by argillaceous soils, when exposed in their natural 

 condition, but not when they were sterilised. He also found gain 

 when the natural soils were enclosed. He considered the results 

 showed that there was gain of nitrogen quite independently of any 

 absorption of combined nitrogen ; in fact that there was fixation of 

 free nitrogen due to living organisms. He further considered that 

 such gains, not only serve as compeusation for exhaustion by cropping, 

 &c., but explain how originally sterile argillaceous soils eventually 

 become vegetable moulds. 



He also made experiments on the fixation of free nitrogen by 

 vegetable earth supporting vegetation ; and he found that there was a 

 gain about equally divided between the soil and the plant, the latter 

 having taken it up from the soil, which he considers is the true source 

 of gain. 



The results obtained under the influence of the silent discharge in 

 bringing free nitrogen into combination with certain vegetable prin- 

 ciples, of course owed their special interest to the inference that thus 

 free nitrogen might be brouglit into combination within the soil, or 

 within the plant \ but M. Berthelot subsequently considered it doubtful 



