412 Report of the Mycologist of the 



in no case were any gas bubbles formed. In fermentation tubes 

 containing two per cent of the above sugars in bouillon there 

 was an abundant growth but no gas was formed. 



'Need of oxygen. — The organism is a facultative anaerobe, grow- 

 ing almost, if not quite, as readily in air which has been robbed 

 of its oxj'gen by Buchner's pyrogallic acid method as it does in 

 normal air. The color, however, is a lighter shade of yellow. 



Temperature relations. — Under this head it can only be said that 

 it grows vigorously at all temperatures between 21° and 30° 0. 

 The thermal death-point has not been determined. 



Behavior toward stains. — It takes the basic aniline stains read- 

 ily, staining uniformly throughout. 



Relation to light. — It is not injuriously affected by diffused light 

 but exposure for a few hours to direct sunlight kills it. Over the 

 cover of an ordinary Petri-dish containing a culture of the or- 

 ganism on potato agar, there was pasted a piece of black cloth 

 which had at the center a* circular hole of 1.8 cm. in diameter. 

 The Petri-dish was then placed in bright sunlight for three hours, 

 after which it was incubated for 96 hours at a temperature of 

 about 23° C. The yellow bacterial colonies came up thickly all 

 over the agar except at the center, directly underneath the hole 

 in the black cloth. Here there were just a few colonies, most of 

 the germs* on this area having been killed by exposure to the eun. 



Plate XVI, fig. 2, is from a natural-size photograph of the cul- 

 ture with the cover removed. It will be seen that the circular 

 area over which the bacteria are killed has a diameter somewhat 

 greater than that of the hole in the cloth. This is due to the fact 

 that the rays of sunlight did not strike the cover at right angles. 



PATHOLOGICAL HISTOLOGY. 



As already stated, the organism occurs in the vascular system 

 throughout the entire plant. It is never found in the parenchyma 

 cells, but in the fibro-vascular bundles exclusively, and is there 

 probably confined to the vessels. There is no disorganization or 

 discolorationf of any of the tissues. 



•Prof. H. Marshall Ward has published a very interesting paper entitled, Action of 

 Light on Bacteria. IIL Philosophical Trans, of the Soc. of London. Vol. 185, Part II, 

 pp. 961-98C. 3S94. On page 964 he makes some suggestions as to why (in experiments 

 like the above) the germs on the exposed area are not all killed. 



t The blackening of the fibro-vascular bundles, a not uncommon occurrence, is not 

 •due to the action of the corn bacterium. 



