8 Agricultural Bacteriology. 



have air, or rather oxygen. The bacteria are no excep- 

 tion to this rule. Many forms known as aerdbes (liv- 

 ing in the air) can grow only in the presence of oxygen. 

 A smaller group known as anaerobes (living without 

 air) grow only in the total absence of free oxygen. 

 These forms must, however, have oxygen, but their only 

 available source is the combined oxygen which they se- 



FIG. 5. PHOTOMICROGRAPH OF ANTHRAX BACILLI. 



The chain-like arrangement is characteristic of this 

 organism. Each member of the chain is an indi- 

 vidual bacillus. Magnified 1,000 diameters. 



cure from organic substances like sugar. An interme- 

 diate type is able to live and grow under either condi- 

 tion, i. e., in the presence or absence of free oxygen 

 /These are called facultative anaerobes. 



Moisture supply of bacteria. No cell growth of any 

 kind can take place without moisture. Bacterial 

 changes go on most rapidly in the presence of an abun- 



