THE NITROGEN CYCLE 221 



1 gram potassium hydrogen phosphate ; 

 | gram magnesium sulphate ; 



trace of calcium chloride ; 



2 grams sodium chloride ; 

 1000 c.c. water. 



Twenty c.c. of this solution were placed in a flat-bottomed 

 flask and a little freshly washed magnesium carbonate added, 

 the flask was closed with cotton wool and sterilised ; 2 c.c. of a 

 2 per cent, solution of ammonium sulphate were then added 

 and the whole inoculated with a little soil. When nitrate 

 development had taken place subcultures were made on to 

 silica jelly. The researches of Frankland and Winogradski 

 have been confirmed by other investigators. 



From the detailed work of Boullanger and Massol, it appears 

 that there are two well-defined organisms which convert 

 ammonia into nitrites. Nitrosomonas, which is a fairly large, 

 nearly spherical organism, exists in two varieties, one the 

 form usually found in Europe, and the other in certain soils 

 occurring in Java. There is also a smaller form known as 

 nitrosococcus. 



The nitric organism is a very small bacterium whose length 

 somewhat exceeds its breadth. 



These two organisms, the nitrous and the nitric, work 

 together in nature, and neither can do its work without 

 the help of the other ; the nitric organism is incapable of 

 directly oxidising ammonia, and the nitrous organism cannot 

 carry the oxidation of ammonia farther than the stage of 

 nitrite. A very important consequence of this differential 

 action is seen in the changes which take place when sewage 

 matter is discharged into sea water ; the nitrifying organism 

 under these conditions is either actually destroyed or rendered 

 inactive. Dr. W. E. Adeney gives the following figures for the 

 results of spontaneous oxidation of sewage, and comparative 

 mixtures of sewage and fresh water, and sewage and sea water, 

 respectively : 



