NITROGEN OF ThE AIR IN VEGETATION. 223 



period of exhaustion and poverty to the soil. A proper and 

 lasting advantage cannot be expected from the use of nitrates. 



DOES THE NITROGEN OF THE AIR TAKE PART IN VE- 

 GETATION ? 



Priestley and Ingenhouss assumed that plants possess the 

 power of assimilating the nitrogen of the air. The former states 

 that a specimen of Epilobium hirsutum kept under a glass globe 

 of ten inches in height, and of one inch in width, absorbed within 

 a month f of the air contained in it. 



These experiments have been repeated by Saussure with every 

 care (Recherches, p. 189), both in pure nitrogen and in atmo- 

 spheric air, exactly according to the method described by Priest- 

 ley, but the results were quite the reverse. Saussure observes, 

 " I have continued the experiments for a long time, but I never 

 could detect a diminution of the nitrogen. The same was the 

 case with all kinds of plants which I submitted to the same expe- 

 riment. Plants, therefore, do not sensibly diminish the bulk of 

 the air ; and these experiments are confirmed by those of Wood- 

 house and Sennebier." 



Hence, we have not any direct proof for the opinion, that the 

 nitrogen of the air is converted into a component part of a plant 

 by its vital processes. In the present state of our knowledge, 

 indirect proofs are equally wanting. 



Many writers on agriculture cite, as decisive proofs of the 

 assimilation of the nitrogen of the air by plants, the experiments 

 of Boussingault, but their interpretation in favor of this view is 

 not supported by facts. This distinguished philosopher instituted 

 a number of experiments in order to decide the question regard- 

 ing the origin of nitrogen in plants, and we give the results of 

 these experiments in his own words (Ann. de Chimie et de Phy- 

 sique, lxix.) : — 



" I believe that I have proved by numerous experiments, that 

 the nitrogen of a rotation of plants is greater and often much 



