260 



BACTERIAL DISEASES OF PLANTS 



sho^vn in Figs. 208 and 209. The organism is white on most 

 media but on Soyka's milk rice it is pale pinkish cinnamon 

 verging toward vinaceous pink in old cultures (R2). Streaked 

 on slices of raw potato it grows rapidly and characteristically, 

 forming a white slime surrounded by a dark (black or brown) 

 border in the disintegrating flesh of the potato. The disin- 

 tegrating potato shoots also are often very black. Bouillon is 



'^ 



Fig. 197. — Base of Fig. 193, 2 days later. The mother tuber, the young tubers 

 and the woody base of the stem are still sound. 



clouded very quickly and gelatin stabs develop a prompt 

 funnel of liquefaction. Potato juice clouds quickly even in 

 the absence of air (closed end of fermentation tubes) but no 

 gas is formed. Ethyl alcohol in peptone bouillon retards 

 or hinders growth (Fig. 210A). The organism does not form in- 

 dol, and does not grow in Cohn's solution. It produces a non- 

 volatile acid from dextrose, saccharose, lactose, galactose, and 



