272 BACTERIAL DISEASES OF PLANTS 



If fermentation tubes are not available, shake-cultures 

 may be made in litmus-peptone agar containing 5 per cent of 

 the carbon compound to be tested (examine early and frequently 

 for gas-bubbles and change of color). Study behavior in potato 

 juice in fermentation tubes. The closed end should cloud. Is 

 any gas formed? I have never seen any. Test suitable cul- 

 tures for indol, for hydrogen sulphide. What is the nature of the 

 acid, or acids, formed by this organism? Can they be driven 

 off by boiling (test the vapor with neutral litmus paper and ob- 



FiG. 209. — Small buried colony of Bacillus phytophthorm (Appel I) after 

 5 days in gelatin at 16°C. The fringe looked like individual bacteria but con- 

 sisted of lenticulate colonies as determined by staining in situ. Colony about 0.4 

 mm. in diameter. Not all the buried colonies showed this fringe. 



serve the litmus reaction of the concentrated fluid)? Is lactic 

 acid produced? Determine toleration of acids. The organism 

 is sensitive to acids (Appel). 



3. Non-nutritional Environjnent. — Effect of heat? of dry air? 

 of sunlight? of freezing (salt and pounded ice)? of salted bouil- 

 lons (try 5 per cent first)? of chloroform in bouillon? of weak 

 acids? of sodium hydrate (try — 40 first)? of germicides? 



Can you get any growth on culture-media at 5°C. or at 

 40°C.? Try several sorts, e.g., potato broth, peptone-beef 



