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. 



