148 ATLAS OF BACTERIOLOGY. 



leguminosse and may be cultivated from them. From 

 the different forms of leguminosse we obtain different 

 races of the bacteria, each one being especially 

 adapted to one form of leguminosse; not every race 

 is able to produce the knobs in every form of the 

 vegetable. There are also "neutral" bacteria, found 

 free in the soil, which are not specially adapted to 

 any form of the leguminosse and which are able to 

 produce knobs in very different forms of the vege- 

 table. 



With the aid of these root knobs, which are due to 

 the immigration of the root bacteria, the leguminosse 

 are able to furnish crops which are rich in nitrogen 

 from a relatively sterile soil which is very poor in ni- 

 trogen. The manner in which the absorption of 

 nitrogen takes place is still entirely unknown. It is 

 claimed that the swollen zooglcea form of bacteria 

 (bacteroids*), almost always observed in the knobs, 

 is alone able to absorb nitrogen. Recently it seems to 

 have been proven that even without the aid of legu- 

 minosse knob bacteria living free in the soil are able 

 to absorb elementary nitrogen (for a detailed resum6 

 of the present status of the question, see Stutzer : C. 

 B., Part II., Vol. L, p. 8). 



12. Production of Acids from Carbohydrates. 



As Theobald Smith showed (0. B., XVIII., No. 1), 

 the formation of free acid is only possible on a 

 saccharine nutrient medium. Its production upon 

 ordinary bouillon takes place only when the latter 



* These bacteroids assume the most bizarre shapes, networks, 

 forks, stars. 



