THE BLACK ROT OF CRUCIFERS: CULTURAL CHARACTERS 155 



Cultural Characters. — Thin-sown agar plates (Figs. 89 to 91), 

 streaks and stabs; gelatin, ditto. Behavior on steamed potato- 

 cylinders standing in water (contrast with No. III). Why is 

 the growth on potato so prolonged? Test for reducing sugars. 

 Growth in Dunham's solution contrasting with Bacterium phas- 

 eoli (Fig. 92). Behavior in bouillon, nitrate bouillon, Cohn's 

 solution, Uschinsky's solution, milk, lavender-colored litmus 

 milk (Fig. 93), peptone water in fermentation tubes with all 

 the common sugars and alcohols. Can you find any that will 



Fig. 96. — Cross-section of the root of an inoculated turnip showing Bacterium 

 campestre occupying a small bundle. Cell walls swollen. X about 600. 



induce it to grow in the closed end of a properly constructed 

 fermentation tube? What is the nature of the yellow pigment? 

 Try extraction with solvents — ^alcohols, ethers, chloroform, ben- 

 zine, benzole, carbon bisulphide, etc. 



Non-nutritional Environment. — Can you obtain growth in 

 bouillon at 9°C. and at 37°C.? Determine maximum tempera- 

 ture for growth, and minimum; resistance to dry air (on cover 

 slips, or silk threads, and on baked turnip or cabbage seed); 

 effect of chloroform in bouillon (contrast with No. Ill) ; killing 



