THE FUNGI WHICH CAUSE PLANT DISEASE 



49 



Gas only in mannite and lactose. Nitrate reduced to nitrite. 

 Opt. 25-28°. T. D. P. 54°, 10 min. 



It was found constantly associated with a type of potato disease 

 which Harrison regarded as distinct from black-leg and from the 

 disease caused by B. 

 solanacearum. It was 

 repeatedly isolated 

 from diseased tubers, 

 stems and leaf veins 

 and occurred in prac- 

 tically pure culture in 

 freshly infected tissue. 



The organisms first 

 appeared in the ducts 

 and thence invaded 

 the surrounding tis- 

 sue, dissolving the 

 middle lamellae and 



'^'■prbifi'jSig,'^ VkK^ e s^ ^. 



Inoculations of pure 

 cultures into healthy ^^°- 32.— B. 

 plants produced char- 

 acteristic lesions and the organism was reisolated. Characteristic 

 enzymic action was observed on placing precipitated enzyme on 

 slices of potato. 



B. sorghi Burr."* Rods 0.5-1 (usually 0.7) x 1-3 (usually 

 1.5) n, cylindrical or oval, motile, spore-bearing, non-liquefying. 

 Colonies on agar, white to pearly. In broth with a white smooth 

 membrane. 



The bacillus was recognized as the cause of a sorghum blight 

 by Burrill and this view was confirmed by Kellerman & Swingle 

 through "^ inoculation experiments. 



B. spongiosus A. & R. ^^^ causes gummosis of cherry in Ger- 

 many. 



B. subtilis (Ehr.) Cohn. 



Straight rods, often united in threads, 0.7 x 2-8 ii. Sporiferous. 

 Spores central or lying near one pole; germination equatorial. 

 Flagella, 6-8, peritrichiate; gelatine liquefied; gelatine colonies 



solanisapnis, from 

 After Harrison. 



hours. 



