44 



Nature-Study Agriculture 



The work 

 of bacteria 



The 



W. T. Skilling 



FIG. 27. Peanut plant, a legume. After the flowers of the peanut are fertilized, 

 their stems (peduncles) bend over and the pods develop in the ground. 



of soil renewal is the one that depends upon the action 



of bacteria. The subject is so important that we need 

 ^ consider it at some length . 



Nitrogen is more likely than any other substance to 

 be deficient, in soils, and, as plant growth is so utterly 

 dependent upon this food, any means of supplying it or 

 retaining it should not be neglected. 



A question As soon as chemists began to investigate the materials 

 of which soil is composed, they found that rocks, which 

 by their disintegration produce soil, contain almost 

 no nitrogen. An analysis of vegetable materials grown 

 upon the soil, especially the grains and all seeds, revealed 

 quantities of nitrogen in their composition. Where did 

 the plants get it? 



