286 FORMATION OF SLIME OR GUM BY RHIZOBIUM LEGUMINOiARUM, 



0-25 c.c., a permanent alkalinity was only obtained when 1 c.c of 

 alkali per 100 c.c. had been added. The normal acidity of the 

 medium is so weak (100 c.c. = - 05 c.c. N/1) that it need not be 

 taken into account. 



The increased yield obtained by the addition of small quantities 

 of alkali indicate that the faint alkalinity of the soil would not 

 diminish the slime-forming faculty of the bacterium. 



In connection with the possible physiological variation of races 

 found in the nodules of different species of plants, it is essential 

 to know whether or not the bacteria obtained from one and the 

 same plant vary from one another. This point was investigated 

 with microbes from the nodules of a Robinia pseudacacia with 

 the result that the bacteria were found to be of one race. The 

 experiments illustrating this are the following : — 



Robinia Rhizobia with various Forms of Nitrogen. 



Sacch 2%, sod.succinateO'2%, agar 2%, and 



Rl 



R2 



R3 



R4 



5 



9 

 9 



R5 



5 

 9 

 8 



R6 



5 



11 



9 



Ammonium sulphate, - 04% ... 



Asparagin, 0-035% 



Potassium nitrate, 0'054% 



5 

 10 

 10 



5 

 9 

 9 



5 



9 



10 



Robinia Rhizobia with various Sugars. 



Asparagin - 04%, sod.succ.0"2%, agar2%, and 



Maltose 

 Saccharose 

 Dextrose 

 Galactose 



R2 



R3 



R4 



R5 



R6 



16 



22 



14 



22 



19 



8 



8 



6 



9 



9 



16 



16 



13 



10 



16 



7 



6 



6 



6 



6 



This was also found to be the case with two bacteria obtained 

 from nodules of different plants of Pisuin sativum in March. 

 AVhen tested together, the activities were similar. But on the 

 other hand, I have obtained races from a single nodule of the 

 Blue Lupin which differed from one another morphologically mid 

 in their staining properties. 



The differences led me to examine them further to see if they 

 were physiologically different. Morphologically the races were 

 as follows : — 



