406 



A TEXTBOOK OF BOTANY 



[Ch. X 



in ripening cheeses, while yet others are concerned in the 

 ripening of stored tobacco. In all these cases the changes 

 are preventable by conditions which inhibit the activity of 

 the Bacteria, — a low temperature being one. 



O-v- 



<§® 



i 



s> 



\* K. 



\ 



Fig. 278. — Typical and important economic forms of Bacteria; all 

 magnified 1000. 



Upper row, Bacillus vulgaris, putrefactive, in proteins (meat) ; Bacterium 

 aceti, fermentative, alcohol to vinegar ; Bacillus radicicola, nitrogen-fixing, 

 in tubercles of Leguminosae, shown in active condition, and as swollen and 

 distorted to bacteroids; Pseudomonas europcea, nitrifying, in soil. 



Second rO w, pathogenic forms ; Coccus forms, of pus ; Pneumococcus, of pneu- 

 monia ; Bacillus, of diphtheria; Bacillus, of tetanus (lockjaw), with spores. 



Third row, also pathogenic ; Spirillum, of cholera ; Bacillus, of typhoid ; 

 Spirochete, of relapsing fever. (Drawn from various sources, the pathogenic 

 forms from microphotographs by Muir and Ritchie.) 



Disease Bacteria. These cause most of the worst diseases 

 in animals including man. They are typically parasites, 

 living in the tissues or blood of their hosts, where they pro- 

 duce injury and death. They have diverse forms, often 

 recognizably characteristic (Fig. 278). They produce their 







