CHAPTER IV 

 AS NITROGEN GATHERERS 



Soil not dead but alive. — Until recently soil was 

 considered dead, inert matter, but now we know it 

 is teeming with life. It is full of countless millions 

 of bacteria, some favorable to the farmers, some 

 neutral, and still others unfavorable. One of the new 

 problems of scientist and farmer alike is to learn 

 more of the action and history of these bacteria. 

 By knowing their character and mode of develop- 

 ment it will thus become possible to encourage the 

 growth of favorable ones in the soil, and hold back 

 the unfavorable. We are coming to believe that in 

 the soil there is a continual warfare among the 

 hundreds of specific bacteria and that, as Darwm 

 says, it is the survival of the fittest. 



Only a few of these bacteria have been separated 

 from their associates and studied sufficiently to 

 know their life and character. Much has been done 

 in the past few years with the particular form of 

 bacteria closely united with leguminous crops, such 

 as beans and clover. Hellriegel in 1888 published 

 deductions made from his studies, which showed 

 conclusively that great numbers of microscopic 

 forms of life can be found on the roots of legumi- 

 nous plants, forming upon them tubercles in which 

 these organisms live and are enabled to draw from 

 the soil air the free nitrogen which the plant so 

 much needs. There are forms of tubercles which 

 live on peas, beans, clovers, and other members of 

 the legume family. The tubercles on the bean plant 

 are exceedingly valuable friends to the bean grower. 



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