230 



BACTERIAL DISEASES OF PLANTS 



X 





FIG. 171. Calla lily rot, due to 

 needle-pricks introducing Bacillus caro- 

 tororus. Leaf-stalk inoculated 48 

 hours at X. The rot extended intern- 

 ally beyond Y. Another leaf-stalk of 

 the same series rotted entirely across 

 and fell over the third dav. 



In potato tubers a protec- 

 tive layer of cork is often devel- 

 oped under the rotting area (Fig. 

 174). In the shoots of potato it 

 is not partial to the vascular 

 system but nevertheless may 

 sometimes be found in vessels 

 at a considerable distance above 

 the place of inoculation (Fig. 

 175). 



Cause. The cause of this dis- 

 ease is Bacillus carotovorus L. R. 

 Jones. This is a gray- white, 1 

 non-capsulate, non-sporiferous, 

 actively motile (2 to 5 flagel- 

 late), peritrichiate (Fig. 176), 

 slowly liquefying (gelatin, but 

 not coagulated egg albumen or 

 Loffler's solidified blood serum), 

 nitrate reducing, milk curdling 

 (by an acid), aerobic and facul- 

 tative anaerobic, gas-forming 

 (with muscle sugar, dextrose, 

 saccharose, lactose and mannit 

 but not with glycerin nor with 



1 Wormald says yellow on Soyka's 

 milk rice (.1 c.). The quality of white- 

 ness is variable as is that of any other 

 color. I agree with Wormald that it is 

 yellowish in contrast with the pure white 

 of the rice medium, about as yellow as 

 steamed potato cylinders, but I would 

 call these white rather than yellow or 

 more exactly following R 2 nearly pale 

 cream color, becoming cream color in old 

 cultures. It is a matter of opinion. 

 Very few white organisms are as white as 

 white rice but nothing would be gained 

 by calling all of them chromogens. For 

 preparation of this useful medium see 

 Eyre's Bacteriological Technique. 



