BLACK ROT OF POTATO : NON-NUTRITIONAL ENVIRONMENT 273 



Fig. 210. — A. Bacillus phytophthorus in +15 peptone-beef bouillon with 

 varying per cents of ethyl alcohol (4 to 7 per cent). Clouded check tube at the 

 right, time 6 days. The others clear. B. Bacillus carotovorus (old 3a) ditto. 

 All showing growth. The white at the bottom of the tubes is a reflection, not a 

 precipitate. C. Same as B, but photographed against a white background. 

 Introduced to show how the camera may deceive. 

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