J. H. Gilbert— Points in connection with Vegetation. 183 



the formation of nitric acid within it ; but, on the contrary, the 

 soil lost a port <3 nitrogen. 



Since the delivery of this lecture, M. Berthelot (Compt 

 Rend., t. lxxxii, p. 1357) has stated that in experiments in 

 which he exposed moistened cellulose to an electric current in 

 an atmosphere of nitrogen, he found nitrogen taken up, and a 

 fixed nitrogenous body formed. Referring to the last men- 

 tioned experiments of M. Boussingault. and his conclusions 

 from them, M. Berthelot objects that the soils being in closed 

 glass vessels, the intervention of atmospheric electricity was 

 excluded, and the conditions of the experiments were, so far, 

 unlike those of a natural soil. 



Being very desirous to know the present opinion of M. 

 Boussingault on the various points involved in this important 

 question of the sources of the nitrogen of vegetation, I wrote 

 to him shortly after undertaking to give this address, and asked 

 whether he would be kind enough to favor me with a state- 

 ment of his views on certain points. Unfortunately his reply 

 did not reach me until after the delivery of the lecture ; but, 

 with his permission. I am now enabled ' to contribute a very- 

 valuable a< I ission in the form of a translation 

 of the more essential parts of M. Boussingault's letter. He 

 says :— 



" (1.) In confined stagnant air, or in air moving through a 

 closed apparatus, after previou- t»U contain- 



ing carbonic acid, plants growing in a soil destitute of nitro- 

 genous manure, but containing the mineral substances indis- 

 pensable for the vegetable organism, do not assimilate the 

 nitrogen which is in a gaseous state in the atmosphere " 



"(2.) In the open air, in a soil destitute of nitrogenous man- 

 ure, but containing the mineral substances necessary for the 

 vegetable organism, plants acquire very minute qua; 

 nitrogen, arising, no doubt from minute proportions of fertiliz- 

 ing nitrogenous ingredients carried by the air, ammoniacal 

 vapors, and dust, always containing alkaline or earthy nitrates." 



"(3.) In confined stagnant air, or in air renewed in a closed 

 apparatus, a plant growing in a soil containing a nitrogenous 

 manure, and mineral substances necessary for the vegetable 

 organism, or in fertile vegetable earth, does not assimilate free 



"(4.) In field culture, where dung is applied in ordinary 

 quantities, analysis shows that there is more nitrogen in the 

 crops than was 'contained in the manure applied." 



"This excess of nitrogen comes from the atmosphere, and 

 from the soil." 



. "(A.) From the atmosphere, because it furnishes ammonia 

 in the form of carbonate, nitrates or nitrites, and various kinds 



