72 



DRY FARMING 



Certain plants, the legumes, have the ability when 

 inoculated to draw upon the air for nitrogen. Red 

 clover, sweet clover, alfalfa, peas, beans, and vetch are 

 examples of leguminous plants. These plants do not have 

 the power in themselves to take up free nitrogen gas. 

 It is through certain bacteria, the nodule bacteris, which 

 live in the soil that this is made possible. These bacteria 



Fig. 25. — Nodules on the Roots of Alfalfa. 



These nodules are the homes of millions of alfalfa bacteria which gather 



Srogen frS.! the air and turn it over to the plant.-Courtesy Wisconsin 



Agricultural Experiment Station. 



attack the root-hairs of the legume plant, causing the 

 formation of gall-like structures called nodules upon 

 the roots. In these nodules the bacteria live and mul- 

 tiply, extracting from the plants the sugars and 



