CAUSE AND NATURE OF CROWN-GALL 



25 



the infection from the points inoculated. At each of the inocu- 

 lations above ground galls appeared, but they were not so large 

 as those below the surface of the soil. 



AN EXPERIMENT WITH WATER CULTURES. 



In December, 1898, two healthy 

 seedlings were cut back to small 

 cuttings and placed in jars parti- 

 ally filled with water. Incisions 

 were made at the crown a few 

 inches above the water. These 

 jars were kept in the laboratory 

 for two months, the water was 

 changed about twice a week, and 

 as the room was kept at a fairly 

 low temperature the growth of 

 the plants was not seriously dis- 

 turbed. Nineteen days after in- 

 oculation the first evidences of 

 the gall became visible on one of 

 the plants. In another week the 

 gall was fully four millimeters in 

 diameter. The gall on the other 

 plant did not become apparent un- 

 til the twenty-sixth day. These 

 galls grew rapidly, and, as they 

 were not in contact with water or 

 moist soil, they were compara- 

 tively free from saprophytic 

 fungi, and provided excellent 

 material for microscopical study. 



1 Fig. 7.— Almond seedling grown as a 



One Of the Seedlings, Six Weeks cutting in water culture, showing a 

 after inoculation, is illustrated in developing gall six weeks after inocu- 



lation 



Fig. 7. 



