224 



BACTEKIAL DISEASES OF PLANTS 



the cells one from another by dissolving the middle part of the 

 cell- wall, which is of a different composition from the outer part. 

 The protoplasm of such separated cells is collapsed and dead, but 

 the bacteria are not found inside the cells except in late stages 

 of the disease. 



The first indications of disease in a carrot root are the ap- 

 pearance of water-soaked (translucent) places around the in- 

 fected wounds. These spots are visible in from 18 to 36 hours 



FIG. 164. Bacillus carotovorus L. R. Jones, streaked for 3 days on raw carrot. 

 Kept on the table at 23C. in a large covered dry culture dish. The inoculation 

 was from a rotting raw potato which was inoculated from a gelatin colony. The 

 carrot was first washed, then soaked in 1:1000 mercuric chlorid water, and cut 

 with a cold sterile knife. The left (check) part remained sound. 



after inoculation when the roots are held at 20 to 24C. With- 

 in two or three days this tissue breaks down, shrivels and exudes 

 drops of a gray fluid swarming with the bacillus. Sometimes a 

 thin, gray bacterial film also covers the surface. When a 2- 

 mm. loop of a bouillon culture is placed on a slice of carrot in a 

 covered Petri dish the water-soaked appearance may sometimes 

 be seen in 6 hours at 20 to 23C. In nature the rot usually 



