36 A SOFT ROT OF THE CALLA LILY. 



DIFFUSED LIGHT. 



Diffused lioht had no effect upon the development of the orj,^anism 

 in an}- of the media used, i. e., beef broth and other liquid media, 

 clouded or otherwise, showed the presence of the organism as readily 

 under one condition as the other, and in the agar plates the colonies 

 formed as quickly and grew as rapidly in difl-used light as in the dark. 



DIRECT SUNLIGHT. 



To determine the effect of direct sunlight upon the organism several 

 tubes, each containing 10 c. c. of agar, were inoculated and poured 

 into thin petri dishes. One-half of each dish was covered with black 

 paper and the dishes Avere then exposed to the direct sunlight. Some 

 of the dishes were removed from the direct sunlight at the end of live, 

 ten, fifteen, twenty, and sixt}- minutes. In those dishes that were 

 exposed five minutes only, colonies appeared in all points of the plate 

 in twenty hours. The colonies appeared just as readily and grew just 

 as rapidly in the exposed as in the unexposed part of the plate, but 

 were a little less numerous, showing that a few of the organisms had 

 been killed by the direct light in five minutes. In the plates that 

 were exposed ten minutes colonies appeared in the covered part of 

 the plate within twenty-four hours, but none appeared in the exposed 

 part of the plate until nearly forty-eight hours after being placed 

 in diff'used light. The colonies which finally formed in the exposed 

 part were much less numerous than those in the shaded part. In the 

 covered part of the plate that w-as exposed fifteen minutes colonies 

 appeared within twenty hours, but no colonies appeared in the exposed 

 side, even at the end of a week, except a few around the edge of the 

 plate, Avhich were apparently protected slightly either b}'^ the shadow 

 of the margin of the petri dish or by the organism being several deep 

 around the margin of the plate, so that the upper layers protected 

 those below from being destroyed by the direct rays of the sun. The 

 same was true of the plates exposed twenty minutes. It appears, there- 

 fore, that from five to fifteen minutes of direct sunlight are sufficient to 

 destroy the life of the organism, but that a very slight protection only 

 is necessaiy to prevent them from being destro3'ed. Even in the 

 plates exposed for sixt}- minutes the organisms around the margin 

 of the plate were likewise protected. In all cases colonies appeared 

 close to the dividing line between the exposed and the shaded part of 

 the plate, and growth extended in every instance from these marginal 

 colonies into the exposed part of the plate, showing the characteristic 

 radiation of the colonies w hen not crowded. 



EFFECT OF NITROGEN. 



Several tubes of beef broth were inoculated with the calla-rot germ 

 and the tubes were placed iiiuuciliately in a jar from wliicli the oxygen 



