12 A SOBT ROT OF THE CALL A LILY. 



investigation, it has been deemed best to place the following results 

 before the public, with the hope that the suggestions herein contained 

 ma}' ])e of value to the industry. 



CAUSE OF THE CALLA ROT. 



Upon examining microscopically the decayed portions of the calla 

 corms m3'riads of bacteria were found to be present. In order to 

 obtain cultures of the organism in the best possible condition a partly 

 decayed corm was thoroughly washed with <"ap water, then with cor- 

 rosive sublimate (1 part in 1,00(J), and afterwards with distilled water. 

 A small opening was then made Avith a sterile knife through the sound 

 part of the corm into the inner marginal part of the decayed spot. A 

 little of the soft tissue just at the border between the decayed and 

 healthy portions of the corm was obtained on a sterile needle and 

 placed in sterile beef broth. Agar plates were then made from this 

 culture, and but one kind of colon}' was obtained, indicating that the 

 organism was present in the recentlv decayed portion of the corm in 

 a pure culture. A few days after the colonies had formed, subcultures 

 were made in beef broth and minute portions of these were introduced 

 into various parts of healthy callas. The inoculations were made by 

 placing a drop of the beef-broth culture on the part of the plant to be 

 inoculated, and with a sterile needle punctures were made through 

 these drops into the tissues of the plants. For control, punctures 

 were made in similar parts of healthy plants without adding the broth 

 culture. In a few days the inoculated spots had turned brown and 

 decay had begun, while the controls in all cases remained healthv. 

 Plate cultures were again made from the inoculated spots after decay 

 had })egun, and apparently the same organism in pure culture was 

 obtained. This process was repeated many times — i. e., until there was 

 no doubt that this organism was the cause of the soft rot of the calla. 



Upon looking up the literature regarding calla diseases it was found 

 that Halsted had discovered a soft rot of the calla corm in 1893." 

 Although Halsted's description is very brief, he undoubtedly refers to 

 the same disease as that which forms the subject of this bulletin. He 

 ascribes the cause of the affection to a bacterium which is found in 

 great abundance in the diseased portions of the corm. A disease of 

 similar nature is also mentioned by Selbv .'' This is referred to as a 

 root rot of the calla, and as no description is given either of the dis- 

 ease or of the organism producing it. it is impossible to determine 

 whether this is the disease now under consideration. The soft rot of 

 the calla and the organism producing it have been observed by Dr. 

 Erwin F. Smith, the pathologist in charge of the laboratory of plant 

 pathology of the United States Department of Agriculture, and bv Mr. 



"Diseases of Calla. New Jei-sey Experiment Station Report for 1893, p. 399. 

 ^Selby. Calla. In Condensed Handbook of Diseases of Plants in Ohio, 1900, p. 21. 



