154 



Plant Physiology 



In the preceding table it is shown significantly that 

 the amount of nitrogen taken up by the leguminous crops 

 reaches a figure averaging far above that of the others. 

 As indicated later, much of this nitrogen is derived from 



FIG. 47. Fertilizer experiments with cereals and grass ; to the right, 

 effect of a nitrate. 



the air through the remarkable activity of the bacteria of 

 the root tubercles ; and in reality it often represents, even 

 with the harvesting of the crop, a soil gain. It would 

 represent a large soil gain if the crop were returned to the 



