138 BACTERIAL DISEASES OF PLANTS 



Cultural Characters. — Growth on thin-sown agar-poured 

 plates — internal structure of surface colonies; growth in gelatin 

 plates; stabs and streaks on agar; do. gelatin. Appearance on 

 steamed potato: this should be wet-glistening, and almost ex- 

 actly the color of the white surface of the potato. A non-para- 



FiG. 70. — Internal markings of agar surface colonies of Bacillus tracheiphilus: 

 a, Isolated from a wilting plant bitten by a striped beetle (1915); b, c, Rand's 

 No. 230 checked up by the writer on cucumber (1918); d, Rand's No. 183 plated 

 in 1919, also checked up on cucumber. All photographed by oblique transmitted 

 light. X 10. 



sitic coccus follower answering to this description on steamed 

 potato may be distinguished by the fact that it reddens litmus 

 milk. Behavior in bouillon; nitrate bouillon; Cohn's solution; 

 Uschinsky's solution ; milk ; litmus milk ; peptone water in fermen- 

 tation tubes with dextrose, with saccharose, with lactose. Can 



