44 A SOFT ROT OF THE CALLA LILY. 



(12) It will not grow at a temperature below 6^ C, nor at a tem- 

 perature above 41*^ C, and grows best at 35° C. 



(13) The life of the organism is destroyed if it is kept for ten min- 

 utes in tubes of beef broth at or above 50^ C. 



(14) Its growth is not affected by diffused light, but direct sunlight 

 will kill the organism in from five to fifteen minutes. 



(15) It will not grow in an atmosphere from which the oxj^gen has 

 been removed, but will remain alive for many months in this condition 

 at a room temperature of 18° to 25° C. 



(16) It does not grow well in an atmosphere of pure hydrogen. 

 (IT) Its growth is very slight in an atmosphere of carbon dioxid. 



(18) When grown on vegetables the end reaction is usually alkaline 



to litmus. 



(19) The organism may remain dormant for many months in partly 

 decayed corms, a condition which enables the disease to be transported 

 long distances and to be held over from year to year. 



(20) The soft rot of the calla may be prevented by a careful selec- 

 tion of sound corms and by changing the soil in the calla beds at 

 intervals of three or four years. 



(21) Brief description of the organism: 



B. aroidex n. sp. A short rod with rounded ends, generally single or in doublets 

 or 4's, but under certain conditions growing in chains. Usual length when taken 

 from a beef-broth culture' 2-1 hours old 2yu-3/^, breadth about 0.5/< and fairly constant. 

 Organism motile, flagella 2 to 8, peritrichiate. Growth white or nearly so on the 

 various solid media. Aerobic and facultative anjerobic. Not a gas producer. 

 Liquefies gelatin; reddens litmus milk, separates the casein from the whey and 

 solidifies the former. Grows slowly on potato cylinders, where it is white with a 

 tinge of yellow% the potato being distinctly grayed. Growth good and vitality long 

 in Uschinsky's solution. No indol produced. Nitrates reduced to nitrites. Methy- 

 lene blue in Dunham's solution is changed to green on addition of grape sugar. Does 

 not grow in nitrogen but remains alive many months. Grows feebly in hydrogen 

 and carbon dioxid. Minimum temperature for growth about 6° C. ; optimum, 35° C. ; 

 maximum, 41° C, thermal death point, 50° C. Surface colonies on agar, round at 

 temperatures near the maximum and minimum, but fimbriate at optimum tempera- 

 ture. 



B. aroklex was isolated from rotting calla corms and is the cause of a soft rot of the 

 corm, petiole, and flower stalk of the calla lily. It also causes a solt, dark colored 

 rot when inoculated into many raw vegetables, such as canot, potato, turnip, radish, 

 cabbage, and cauliflower. It also causes a soft rot of certain green fruits, such as 

 the tomato, eggplant, and cucumber. 



