40 



THE FUNGI WHICH CAUSE PLANT DISEASE 



structans. Harding and Morse, however, believe it specifically 

 identical with B. carotovorus. See p. 42. 



B. atrosepticus v. Hall,^^ was isolated from ducts of potatoes 

 affected with black leg. 



B. avenas, Manns.^^ This is the symbiont of Pseudomonas 

 avenae. See p. 23. 



(Group number 222.2223532.) A very actively motile bacillus, 

 short, rod-shaped with rounded ends, 0.75 to 1 x 1.5 to 2 /i. 



Fig. 20. — Plate culture of B. avenae, on nutrient glucose agar, 

 four days at 30°C. After Manns. 



Gram negative; endospores not observed; flagella many, diffuse, 

 long, undulate; growth on agar stroke rapid, filiform, white, 

 glistening, later somewhat dull, margin smooth, gro\vth rather 

 opaque, turning yellow third day; gelatine not liquefied; broth 

 clouded and on the second day showing heavy yellow precipitate; 

 milk coagulated at end of two weeks with extrusion of whej^; 

 agar colonies round, entire, surface smooth, slightly raised. No 

 gas in dextrose, saccharose, lactose, maltose, or glycerins. Indol 

 production moderate; nitrates reduced to nitrites. T. D. P. 10 

 min., 60°; Opt. 20-30° 



