254 



BACTERIAL DISEASES OF PLANTS 



wilting or a slow yellowing of the lower leaves and a stricter 

 habit of growth in the upper ones, the leaflets of which (Fig. 190) 

 are or may be more or less incurled (upward) . If one examines 

 the base of such shoots they will be found to be black-spotted 





FIG. 191. FIG. 192. 



FIG. 191. Stems of Green Mountain potato inoculated 48 hours at X with 

 Bacillus phytophthorus Appel, from a 2-day agar-streak culture. Stems black and 

 rotting in the pricked area. Hothouse experiment of January 23, 1915. Tubers 

 half grown. Organism from Germany. In the laboratory since August, 1906. 



FIG. 192. Same lot of plants as Fig. 191, but 4 days after inoculation (at A'). 

 Stems black and nearly rotted off in the pricked area; bundles infected upward 

 for long distances and with a brown stain coming to the surface. 



pnd more or less softened (Figs. 191, 192) at the surface of the 

 earth or just below it, and hence the German name Schwarzbe i n- 

 igkeit (black leg). Generally at first this blackening and ulcera- 

 tion are restricted to the base of the stem but upper parts soon 



