Importance of ‘ Nitragin * 5 1 9 
ordinary garden soil, peat, clay or loam inoculation with 
‘ Nitragin ’ is useless and superfluous, whilst upon gravelly 
soils a small increase in crop results from its use. 
These unfavourable results with ‘ Nitragin 5 lead to the 
conclusion that the explanation of the problem of the nutrition 
of Leguminous plants does not depend on the mere presence 
or absence of the nodule-organisms, but that their effect on 
the host is directly controlled by the conditions biological, 
physical and chemical, existing in the soil at any given time, 
so that it is from bacteriology and chemistry that we may 
expect to receive great help in the solution of this difficult 
problem of modern agriculture. 
The Botanical Laboratory, Cambridge. 
May , 1901. 
