4(3 LABORATORY BACTEEIOLOGl'. 



EXEECISB XXXV. 



DESCRIPTION OF PURE CULTURES OF AZOTOBAGTER. 



1. Pure cultures of Az. vinelandii, Az. beijerincki and 

 Az. chroococcum are to be carefully examined and described 

 for future reference. 



2. Make microscopic stained and hanging drop prepara- 

 tions and note the characteristics of the various organisms. 



3. Inoculate into tubes of mannite solution, incubate 4-5 

 days at 20° C. and describe the growth. 



4. Prepare mannite agar plates in the usual way, incubate 

 4-5 days at 20° C. and study the colonies developed. 



5. Inoculate on potatoes and after incubation describe the 

 growth. 



6. Make gelatin stabs, gelatin plates, sugar broth and milk 

 cultures and describe the growth obtained. 



7. Tabulate the results of the examinations. 



