33S ANNUAL REPORT OF THE Oft. Doc. 



1. That ill the soil the nitrifying process was ettected by two dis 

 tinct but closely related organisms; the one converting ammonia into 

 nitrous acid and nitrate, and the other changing the nitrites into 

 nitrates. 



2. That these two processes follow one another in such rapid suc- 

 cession that the production of nitrites is only a transitory phe- 

 nomenon, so that if both the nitrite and nitrate organism be added 

 to sterilized soil the process is completed in the natural way, only the 

 merest traces of nitrous acid appearing. 



The nitrate organism of Wiuogradsky is an oval form about 0.5 

 micromillimetres in length. The nitrite germ varies from oval to 

 spherical and is about twice the size of the former. See Figs. 5 and 6. 



If to a mineral solution containing ammonium salts, a pure cul- 

 ture of nitrite ferment be added, only nitrites will be formed, and 

 these will remain unchanged in the absence of the second nitric fer- 

 ment. If, how^ever, the two organisms be added simultaneously, 

 nitrates will be rapidly formed. 



In 1892, Winogradsky^^ studied the nitrifying organisms of soil, 

 from a number of different localities. Those from several parts of 

 Europe, from Africa, and from Japan, which he considers to be the 

 same organism, he names Nitromonas europea; a second form 

 from Java soil, differing from the first he names N. javenensis. 

 Both of these comprise the nitrite ferments of Wiuogi'adsky; the 

 second nitrate ferment was isolated by Winogradsky from Quito soil 

 and differs from the first not only as to size, as above mentioned, 

 but also by entirely lacking the motility common to the latter. 



The notable researches of Winogradsky have been followed by 

 others which have interest from a controversial standpoint. 



In 1895 Burri and Stutzer^^ isolated from soil a nitrate organism 

 with properties akin to the Quito bacillus of Winogradsky. It was 

 a motile organism, 0.75-1.5x0.5 micromillimeters, growing on silica 

 plates in definite colonies, but also possessing the power to grow on 

 gelatin and to liquefy the medium; said organism according to the 

 writer being able to convert nitrites into nitrates, but losing such 

 power when grown on organic media. 



The above results of Burri and Stutzer, so contrary to those of 

 AVinogradsky, brought forth a vigorous rejoinder from the latter. 

 In this Winogradsky stated that he tested the same earth used by 

 Burri and Stutzer and isolated therefrom his own Nitromonas, and 

 that the latter w^hen tested in bouillon, meat pepton, gelatin and 

 agar failed to grow. He therefore regards the German work as er- 

 roneous. 



In 1897 Stutzer and Hartleb*" appeared with a still more startling 

 series of discoveries in which they not only maintained the ability of 

 the nitrifying organisms to grow in orcranic media, but also showed 



