BACTERIA IN THE INDUSTRIES 173 



poses. Some authorities maintained that it was of unquestionable value in 

 virgin soil. In rich and otherwise favorable soil conditions it is of only 

 slight value. It is maintained that nitragin aids very materially_in 

 developing and ripening the fruit. As becomes evident from careful con- 



PIG. 52. Motile forms of Rhizobium mutabile as they appear in fresh cultures. They 

 are very small, % to %/t in length. 



sideration, the value of this microbic fertilizer depends upon whether or 

 not it will cause an increased development in the number and size of root 

 tubercles over and above those which would develop without the presence 

 of this artificial aid. If the soil is already well supplied with rhizobia 



FIG. 53. Non-motile matured forms"of\R. mutabile as they appear in mature sweet 

 clover root nodules. Most of them^show.the forked ends. This may be considered the 

 normal form of this organism. 



or root tubercle bacteria, as soil would naturally be if the leguminous plants 

 under consideration had been grown in it for one or more seasons, nitragin 

 would in all probability be of little or no value. In any case, the anti- 

 cipated results have not been fully realized, and nitragin is withdrawn from 

 the market, and is no longer manufactured. 



