20 



BACTERIAL DISEASES OF PLANTS 



There is good reason to believe that the black rot of cabbage 

 and Stewart's disease of sweet corn have been disseminated 

 broadcast in the United States in recent years by ignorant and 

 unscrupulous seedsmen. Both diseases are transmitted to seed- 

 ling plants from the seed. The bacterial black chaff of wheat 

 (Figs. 12 to 22) which is widely prevalent in Kansas, Iowa and 



FIG. 13. A single yellow surface colony of Bacterium translucens var. undu- 

 losum Smith, Jones and Reddy, the schizomycete causing black chaff of wheat. 

 A glume isolation on +15 beef-peptone agar from No. 273, Dubois, Nebraska. 

 Photographed by oblique, transmitted light to show internal wave-like markings, 

 surface perfectly smooth. Plate poured July 9, 1917. Photo July 30, Temp. 

 28-32C. X 10. 



other Western States is a seed-borne infection, and so is the very 

 similar barley disease described by Jones, Johnson and Reddy. 

 The yellow disease of hyacinths is carried in the bulb. Potato 

 tubers from diseased fields may infect healthy fields. Apple 

 grafts have transmitted crown-gall. Slightly infected trunks 

 and limbs of trees (hold-over pear blight, walnut blight, canker 

 of the plum) may infect shoots, leaves, blossoms, or fruits 



