BY R. GRBIG-SMITH. 293 



bacteroidal formation. Much, however, depends upon the acidity 

 of the sap of the nodule, which, by making the capsule of the 

 micro-organism more insoluble, brings about the branching 

 condition. The acidity also conduces to the formation of the 

 " infection threads " of the nodule. 



The inconsistency of the results hitherto obtained in the 

 inoculation* of the leguminous crops with bacterial cultures are, 

 probably, in part, at least, due to the fact that the slime-forming 

 function of the micro-organism has not been recognised, and races 

 incapable of forming slime have been taken. Furthermore, the 

 infective material may have, to a great extent or entirely, lost 

 this typical property. But even among those races which form 

 slime luxuriantly, and which are probably the better able to 

 assist the plant, there are to be found differences of character 

 which may be of such a nature as to determine whether the 

 micro-organism is a nodule-former or not. A notable example is 

 the acidophile slime-forming race isolated from the Blue Lupin. 

 Such a race appears to be one which, among all others, is most 

 suitable for producing slime in the nodules of the plant. Races 

 with similar acidophile, slime-forming characters, promise to be 

 most efficient agents to use in the preparation of commercial 

 cultures of the micro-organism. 



Addendum. — When isolating Rhizobium leguminosarum from 

 the Blue Lupin, I found a colony which produced a luxuriant 

 slime upon saccharine media. It consisted of a mixture of three 

 bacteria, viz., Bad. radiobacter, Azotobacter chroococcum and Bac. 

 Uvaniformans. In a synthetic, nitrogen-free medium, the mixture 

 of the bacteria gave 10 % of slime, and a determination of the 



*An experiment upon a small scale was made by Mr. H. W. Potts, 

 Principal of the Hawkesbury Agricultural College, at my request, to test the 

 effect of the infection of Cow Peas with slime-forming bacteria isolated 

 from the Field Pea and Black Tare. The results were negative, but this 

 might be explained by the abnormally dry season, by the unsuitability of the 

 bacteria of one crop for another, or by the presence of a sufficient number of 

 slime-forming bacteria already present in the experimental soil. Probably 

 the last of these conditions prevailed. 



