[JONES] STUDY OF SOME AZOTOBACTER 53 



2. Neisser's Blue. This stain has only a very faint action on the 

 capsules but a strong action on the stainable parts of the organism. 

 Young homogeneous cells are stained a bright blue. Granules of the 

 No. 1 type are not stained, but granules of the No. 2 type are very 

 strongly stained and frequently present the appearance of cocci within 

 pus cells. 



3. Saturated alcoholic solution of Rosanilin Violet. The action 

 of this stain is very similar to that of Neisser's blue but is a little weaker 

 on the stainable parts of the organism and a little stronger on the 

 capsule. 



4. Safranin (Babe's). The action is very similar to that of 

 the Rosanilin violet. 



Of the other stains tried, aqueous fuchsin stains similar parts to 

 the above, but less distinctly. Alkaline methylene blue stains similar 

 parts but very faintly. Carbol fuchsin is unsatisfactory, staining 

 darkly and giving no differentiation. Bismarck brown stains, but the 

 differentiation is not good. Hematoxylin was tried a number of times, 

 but the preparations always washed off during the process. The organ- 

 ism is negative to Gram's; gives the glycogen reaction with iodine- 

 potas-iodide solution, in young cells weakly, old cells strongly, the 

 granules of No. 1 type in the old cells being the parts giving the strongest 

 reaction. Treatment with osmic acid never revealed any fat drops 

 present. 



Temperature Relations. 



25°C. gives the greatest and most rapid growth. 

 37°C. gives very slow growth, the organism increasing in size and 

 changing very markedly in shape but multiplying very slowly. 

 20°C. growth similar to that at 25°C. but slower. 

 0°C. very slow growth occurs. 

 Thermal death point is between 55°-60°C. 



Test tubes containing 10 c.c. of Ashby's solution inoculated sever- 

 ally with loopful of cultures from plate colonies of each variety one 

 week old and four weeks were heated in duplicate for ten minutes at 

 various temperatures from 40°C. to 95°C. All cultures heated to 55°C. 

 and under developed and grew well; all cultures heated to 60°C. and 

 above were killed. 



Fixation of Atmospheric Nitrogen. 



Cultures of each variety in Ashby's solution when one month old 

 gave the nitrate reaction with the phenolsulphonic acid colorimetric 



