BLACK ROT OF THE POTATO: CULTURAL CHARACTERS 271 



organism produce a bad odor on any medium?); What is the 

 early and late behavior of this organism in lavender-colored 

 litmus milk (watch closely from the start) ? On a proper use of 





Fig. 207. — Bacillus phytophthorus (Appel I). On +10 beef-peptone gelatin 

 held for 3 days at 16°C. All but the corona has liquefied. Actual diameter 

 of colony, 1 mm. Margin fringed like Bacillus carotovorus (see Figs. 180, 181). 

 Photographed February 4, 1915. Buried colony below at left. The specks 

 scattered about are due to dust on the eyepiece. 



litmus in milk, consult "Bacteria in Relation to Plant Diseases/' 

 Vol. I, pp. 48, 196. Test shake-cultures in beef-peptone agar 

 (for gas-bubbles which will appear only if muscle sugar is 



# 



Fig. 208. — Bacillus phyiophthorus (Appel I). Small buried colonies from 

 same gelatin plate as Fig. 207 but enlarged about one-third more. One colony 

 out of focus. 



present) ; try peptone water in fermentation tubes with all the 

 common sugars and alcohols. From which is acid only pro- 

 duced? From which both acid and gas? 



