260 uoAv OKors feed. 



were mado of the soil and seed before tlie trial, and of the 

 soil and crop afterwards. 



The analyses show that while in all cases the plants 

 gained some nitrogen beyond what was originally contain- 

 ed in the seed, there wns in no instance any loss of nitro- 

 gen by the soil, and in three cases the soil contained more 

 of this element after than before the trial. Here follow 

 the results. 



No. of Mip. 



1. Lupin,* 



2. Lupin, 



3. Hemp, 



4. Bean, 

 B. Lupin,* 



That the gain of nitrogen by the soil was not due to 

 direct absorption of nitric acid or ammonia from the at- 

 mosphere is demonstrated by the fact that it was largest 

 in the two cases (Exps. 1 and 5) where the experiment was 

 conducted in a closed vessel, containing throughout the 

 Avhole time the same small volume, about 20 gallons, of 

 air. 



In Exp. 4, where the soil at the conclusion contained no 

 more nitrogen than at the commencement of the trial, it 

 is scarcely to be doubted that the considerable gain of ni- 

 trogen experienced by the plant came through the soil, 

 and would have been found in the latter had it borne no 

 crop. 



The experiments show that the quantity of nitrogen 

 assimilated from the atmosphere by a given soil is very 

 variable, or may even amount to nothing (Exp. 3); but 

 they give us no clue to the circumstances or conditions 

 which quantit.itively influence the result. It must be ob- 

 served that this fixation of nitrogen took place here in a 

 soil very rich in organic matters, existing in the condition 

 of humus, and capable of oxidation, so that the soil itself 



Experiments made in confined air. 



