The Relation to Nitrogen 233 



vulgaris, while many common molds, punks, and mush- 

 rooms are among the various fungi inducing decay in the 

 forest. 



127. Nitrification. - - Ammonification is the comple- 

 tion of the first stage in the cycle of changes whereby ni- 

 trogenous matter may be converted to nitrates, the suc- 

 ceeding transformations being as follows : - 



(1) Oxidation of the salts of ammonium into nitrites. 



(2) Oxidation of nitrites into nitrates. 



The production of nitrates (ultimately) from organic 

 matter has been long known and practically carried out 

 by means of the niter beds so much employed a generation 

 or two ago. A process wholly similar in nature has given 

 rise to the natural deposits of niter and is constantly at 

 work in the best arable soils to develop nitrates. 



128. Nitrifying organisms. - - In 1877 it was first 

 determined (Schloesing and Mtintz) that nitrification is 

 effected by bacterial agencies, and Winogradski, Waring- 

 ton, Godlewski, and others have laid bare many impor- 

 tant features affecting the action of the organisms involved. 

 These bacteria are widely distributed in soils and in drain- 

 age or run-off waters. 



The organisms oxidizing ammonia to nitrites (nitrite 

 organisms) are small, oval, motile cells generally included 

 in the genus Nitrosomonas, while those oxidizing nitrites 

 (nitrate organisms) are considered nonmotile and included 

 in the genus Nitrobacter. 



These two types of bacteria are commonly associated 

 in the soil, and all forms seem to exhibit the peculiar 

 physiological quality of being able to make their own 

 carbohydrate food from CO 2 and water. Unlike green 



