It is invariably present in soils, where compounds are formed by nitrifying bacteria.
The chief importance of nitrogenous compounds depends upon their assimilation by living plants, which, in their development, absorb these compounds from the soil, wherein they are formed mainly by the action of nitrifying bacteria.
The discoveries that some species of nitrifying bacteria and perhaps pigmented forms are capable of carbon-assimilation, that others can fix free nitrogen and that a number of decompositions hitherto unsuspected are accom fished by Schizomycetes have ut thequestions of P Y Y, P d nutrition and fermentation in quite new lights.
The nitrifying, nitrogen-fixing, sulphurand iron-bacteria he regards as monotrophic, i.e.
As regards the ammonium carbonate accumulating in the soil from the conversion of urea and other sources, we know from Winogradsky's researches that it undergoes oxidation in two stages owing to the activity of the so-called " nitrifying " bacteria (an unfortunate term inasmuch as " nitrification " refers merely to a particular phase of the cycle of changes undergone by nitrogen).