ALBUMINS OR PROTEINS. 



197 



present were exactly known. Sterilized water was added in one experi- 

 ment, while the others were watered with infusions of powdered nodules. 

 Three months later the air was removed from the cylinders and the amounts 

 of nitrogen present estimated. It was found that it was diminished only 

 in those cases where nodule extractions had been added. Two of these 

 experiments in which root nodule infusions were used gave the following 

 values : 



The nitrogen absorption can be shown even better by the following 

 table. In experiment III there were no root nodules present, whereas 

 I and II contained these: 



These root nodules contain bacteria, as has been proved by Beijerinck.i 

 They live in symbiosis with the cells of the nodules. Beijerinck names the 

 bacillus B. radicicola. It is widely distributed in land and water. Recent 

 investigations indicate that this nitrifying organism is not a separate 

 individual. It seems as if various bacilli are assigned to the different 

 varieties of Papillionacce. Successful inoculations of the nodules have only 

 been possible with closely related members of this family. For instance, 

 we have not succeeded in forming nodules on the robinia roots by means 

 of the bacteria from peas. It is also very interesting to note that Soja 

 Hispida very often fails to produce nodules in European gardens, but will 

 do so when impregnated with Japanese earth. To indicate the impor- 

 tance of these discoveries we may add that the nodule bacteria have become 

 an article of commerce. 



It is problematical whether these nodule bacteria are restricted to the 

 Papillionacce. There are indications that they are also found in other 

 plant species. They are believed to be present in the Rhinantacce, Elceag- 



1 Bot. Zeit. (1888) p. 725. 



