156 



BACTERIAL DISEASES OP PLANTS 



power of sunlight (in thin-sown agar plates); effect of weak 

 acids and alkalis; gf salted bouillons (contrast with Nos. I and 

 III). Vitality on culture-media. 



FOR THE DISEASE. Signs. Determine time between inocu- 

 lation (a, by needle pricks b, through the water-pores) and 

 first local signs of the disease. In case of plants inoculated on 

 the leaf-blade, how long before signs appear in other leaves? 



??*! 







s 



FIG. 97. Like Fig. 96, but shows beginning of a cavity. X 500. 



Contrast inoculations on plants growing rapidly and slowly. 

 In case of inoculations on the petiole, how long before signs 

 appear in its blade? After the infection (blackening) of the 

 water-pore region, how long before the veins of the leaf begin 

 to show the dark stain? Describe the disease. 



Histology. Determine by sections the occupation of the 

 substomatic region in the infected leaf-teeth. Can you trace 



