IDENTIFYING GENERA OF BACTERIA 63 



EXERCISE XXV 



IDENTIFYING GENERA OF BACTERIA FROM THE DUST 

 IN THE AIR AND OBTAINING PURE CULTURES FROM 

 COLONIES 



96. Work for this Exercise Examine and carefully de- 

 scribe the colonies on the plate cultures made by exposing 

 agar and gelatin plates to the air in the last exercise. Deter- 

 mine the number of different colonies and carefully describe 

 each. Explain the reason for variations in the number of 

 colonies on the different plates. 



Inoculate a tube of bouillon from a colony of each genus. 

 Label the inoculated tube with the name of the genus. Make 

 stained cover-glass preparations from a colony of each genus. 

 Mount and label one of each of these preparations to accom- 

 pany the notes. 



