206 



BACTERIAL DISEASES OF PLANTS 



colonies which become darker with age but are always yellow 

 (not orange colored). Katherine Bryan has also isolated a 

 form which spreads on agar. It stains by Gram, but is not acid- 

 fast. It grows copiously in milk with slow coagulation^, form- 

 ing a thick pellicle and a broad yellow rim. A very little acid 

 seems to be produced, as litmus in milk becomes gray or purplish 



FIG. 146. Tomato leaf showing irregular wilting of leaflets due to Aplano- 

 bacter michiganense. Stem inoculation by Mary Katherine Bryan using a round 

 colony. Photographed May 3. 1917. 



red before it is reduced. It grows well on cylinders of steamed 

 potato standing in water, the bacterial layer being pale yellow 

 at first, becoming bright yellow (R 2 , light cadmium), smooth and 

 inclined to spread. In color, the slime of this organism on 

 potato is not unlike that of Bacterium campestre, but the growth 

 is less prolonged. The substratum out of the water is grayed. 

 Its growth in peptone bouillon, and on gelatin- and agar-poured 



