[Vol. 10 



44 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Nutrient broth is promptly clouded, the medium becoming 

 slightly turbid after a few days. The characteristic surface 

 growth is a ring, though in some broths a light pellicle may de- 

 velop. 



Milk is promptly coagulated, the amount of titratable acid 

 produced by the organism increasing steadily for several days. 

 A slow peptonization of the curd begins on the second or third 

 day. 



In Cohn's solution there is no growth. In Uschinsky's solu- 

 tion the growth is copious, but the fluid does not become viscid. 



No indol is demonstrable by the Ehrlich test, in either young 

 or old cultures grown in peptone water made with (1) Witte 

 peptone, or (2) Bacto peptone. Nitrates in nitrate broth are 

 reduced to nitrites without the formation of gas. Ammonia 

 production is feeble to moderate. 



Carbohydrate reactions. — Acid and small volumes of gas are 

 produced from dextrose, galactose, sucrose, maltose, and mannite. 

 The gas-producing capacity is not particularly characteristic. 

 No acid and no gas are produced from glycerin, dextrin, and po- 

 tato starch. Quantitative consumption of the common hexose 

 sugars, glucose, fructose, and galactose, has been demonstrated. 

 Likewise, Hie organism consumes sucrose, lactose, and maltose. 

 A sugar concentration of 0.25 per cent is ample. Diastatic ac- 

 tion is absent, both in respect to starch and dextrin. 



Enzyme 8. — This organism secretes several carbohydrate en- 

 zymes, as is shown by its action on as many different saccharides; 

 cytase also is probably produced. 



The optimum temperature for growth is about 26° C, with no 

 growth at 37.5° C. The organism withstands considerable ex- 

 tremes of cold, being found viable in soil cultures exposed for 

 24 hours to temperatures ranging from — 6.7° to — 28.2°C. 



The blackleg bacillus is quite resistant to drying and remains 

 viable for long periods of time on plain beef agar. 



Virulent strains produce a necrosis of the stem and tubers of 

 the potato. Parenchymatous tissue is almost exclusively af- 

 fected, and a blackening of the diseased tissues is characteristic. 



