The Relation of the Reaction and of Salt Content of the Medium on Nitrifying Bacteria

The fiterature of soil bacteriology is replete with assertions to the effect that soil bactena of value for the maintenance of an appropriate soil condition need an alkaline medium for their proper development. This has been repeatedly emphasized, particularly in connection with the nitrifying and the nltrogen-fixing flora of the soil. Actual evidence substantiating such assertions has never been adduced from experiments, or at least, it has never been presented. This situation is, in part, explained by the vagueness of our old conceptions with regard to the real nature of alkalinity and acidity as applied to biological media. I t is natural, therefore, that studies such as those needed to give the subject a proper status should have lagged behind the rapid development of the methods for determining hydrogen and hydroxyl ion concentrations in the last 8 to 10 years. Even such a recent investigation as that of Stephenson (1) on the relations of nitrification to acidity in soils takes no account of the