CHAP, in The Absorption of Nitrogen 335 



chloride containing as well the other mineral constituents 

 required by green plants would not form any compounds of 

 nitric or nitrous acid, unless the germs present in ordinary 

 soil were allowed access to it, and unless an excess of a 

 salifiable base such as calcium carbonate was present. Under 

 these latter conditions nitrification took place after a vari- 

 able period of incubation. The experiments succeeded best 

 in darkness and at a temperature below 40 C. 



He found that in successful experiments the products 

 were not uniform ; sometimes nitrous acid, sometimes nitric 

 acid, and occasionally both, were produced. The reason 

 for this discrepancy he left undetermined, saying he had 

 not ascertained the conditions leading to the several results. 

 He seems to have regarded the various external factors as 

 playing an important part among those conditions ; but he 

 held them in part, at any rate, to depend upon the state 

 of the germ or ferment in the soil employed. 



In the same year, 1879, appeared two communications 

 from Schloesing and Muntz, in which they claimed to 

 have isolated the nitrifying organism. They described it, 

 gave an account of their method of separation, of its range 

 of action, and of the temperature under which such action 

 is possible, together with a discussion of the influence of 

 other conditions upon it. 



The organism was studied again in 1883 by Duclaux ; 

 he described it as varying considerably, and hence 

 suggested that several -species possess the property of 

 nitrifying ammonium compounds. 



Warington's next paper appeared in 1884, and was chiefly 

 devoted to experiments bearing on the character and be- 

 haviour of the organism. He started with his old observa- 

 tion of the variation of the nature of the products and 

 the explanation of it which he was then inclined to favour, 

 but showed that his experiments of more recent date 

 led him to think the character of the organism was the 



