VITAL PHENOMENA OF BACTERIA. 79 
ammonia into nitrites and the other converts nitrites 
into nitrates. 
Conversion of Nitrous and Nitric Acids into Free Nitrogen. 
This process is performed by a number of bacteria. The 
special nitrate-fermenting bacteria, however, were first 
accurately described by Barri and Stutzer. In their 
exhaustive investigation they first isolated from horse- 
manure two bacteria, neither of which was alone capable 
of producing nitrogen from nitrates, but which together 
in the presence of oxygen, but never without it entirely, 
decomposed nitrates energetically. Later a second 
denificating bacillus was found, B. denitrificans II., 
which by itself was able to produce nitrogen from 
nitrates. 
The practical importance of these organisms is that 
by their action large quantities of nitrates in the soil, 
and especially in manure, may become lost as plant- 
food by being converted into nitrogen. 
Nitrogen Combination. The bacillus radicicola of 
Beyerinck, which was isolated by him, has the power of 
assimilating nitrogen from the air. This bacillus is found 
in the small root-nodules of various leguminous plants 
(pease, clover, etc.), and can be obtained from these in 
cultures. Different varieties exist in different kinds 
of legumes, each kind of legume apparently having a 
special variety of bacteria adapted to it, and not every 
variety is capable of producing nodules in all legumes. 
There are certain “ neutral ’’ varieties, however, existing 
free in the soil and not adapted to any special legume, 
and these seem to be able to form nodules in different 
legumes. 
By the aid of these root-bacteria, which gain entrance 
to the roots and there produce this nodular formation, 
