[Vol. 10 



30 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



moderate clouding; No 170.3 and 197, moderately strong cloud- 

 ing; No. 191, the surface growth a membrane with moderate 

 clouding; and in No. 201 the surface growth was a light pellicle. 



Observations recorded upon the cultural features exhibited by 

 the different strains (except No. 191) as grown in these broths 

 suggest a clue as to the disagreement between all who have cul- 

 tivated the blackleg bacillus as to the character of the surface 

 growth. It was found that the clouding was stronger and the 

 surface growth heavier (a pellicle) in the nutrient broth made 

 from a fresh meat infusion and "Bacto" peptone than in either 

 of the other two nutrient broths used. Moreover, the growth 

 response in the broth made with "Bacto" beef and "Bacto" pep- 

 tone was somewhat more luxuriant than that in the beef extract 

 and Witte peptone broth. The writer concludes that strain No. 

 191 is the only one of the 12 studied in broth that exhibits 

 dissimilarity. 



Agar stroke. — Growth moderate, filiform, somewhat raised, with 

 smooth surface and glistening luster, translucent and somewhat irides- 

 cent, non-chromogenic ; consistency butyrous, some quite viscid; odor 

 absent; medium (color) unchanged. 



On agar slants the cultural features were identical for the 

 strains studied, except No. 191, where the form was spreading 

 and effuse, the surface smooth, and luster dull. 



Potato (cooked). — Growth moderate to abundant, filiform at first, 

 spreading after a few days, slightly raised and flat, glistening, with a 

 smooth to slightly contoured surface ; chromogenesis yellowish white ; 

 odor not strong nor characteristic; color of medium slightly browned. 



Special attention was devoted to the cultivation and study of 

 the cultural features of the blackleg strains on sterilized potato 

 plugs. This was done because of the importance attached by 

 some authors to the cultural characteristics on this medium, in 

 the differentiation of their "species" from others. All the strains 

 studied comparatively by me were quite alike (except No. 191), 

 in so far as can be detected from a study of the growth and cul- 

 tural features on sterilized potato plugs. In No. 191 the growth 

 was scanty, form spreading, surface smooth, dull, and colorless. 



Potato (raw). — Raw potato slabs aseptically prepared as out- 

 lined in a preceding section were used. Preliminary tests indi- 

 cated that infection and growth by the organism took place when 

 the atmosphere of the culture chamber (Petri dish) was moist 

 and when incubated at about 26° C. 



