168 



BACTERIAL DISEASES OF PLANTS 



culture and reexamine), absence of endospores (heat, stains), 

 presence or absence of capsule, occurrence of involution forms, 

 reaction to Gram's stain (diaphragm wide open). 



Cultural Characters. — On agar (Figs. 114, 115), on gelatin, on 

 steamed potato, in bouillon, nitrate bouillon, Cohn's solution, 

 Uschinsky's solution, lavender-blue litmus milk. Fermenta- 

 tion tubes in peptone water with various pure sugars and alcohols. 



Fig. 109. — A larger bundle at the same level as Fig. 1(38, showing Apbinobactcr 

 stewarti occupying many of the vessels. 



Growth in acid plant juices, e.g., green tomato juice full strength 

 and diluted with an equal volume of water (titrate with phenol- 

 phthalein and N/20 sodium hydrate to determine the acidity). 

 Compare with No. II or No. VIII. 



Non-nutritional Environment. — What is the optimum tem- 

 perature for growth? the maximum? the minimum? Can 

 you get any clouding of +15 peptone beef bouillon at 9°C.? 



