EXPERIMENTS WITH THE ROSE ORGANISM. 76 



ROSE ON DAISY. 



Isolation op Organisms. 



On December 10, 1907, 2 rose bushes were found in the propagating 

 greenhouse of the Department of Agriculture with galls 2 inches in 

 diameter on the root below the graft. Plates were poured from the 

 soundest part of one of these galls after proper scrubbing and surface 

 sterilization, i. e., the scrubbed gall was pared with a sterile knife 

 and small selected pieces designed for cultures plunged for about 2 

 seconds into mercuric-chlorid water (1 : 1,000), rinsed in sterile water, 

 and crushed in sterile bouillon for the plates. In three days the 

 typical gall colonies appeared. 



Inoculations of March 18, 1908 (Brown). 



Eight inoculations were made with rose A on daisy plants, 4 on a 

 large yellow-flowered variety and 4 on the Queen Alexandra. One 

 check. 



Result. — March 31, 1908: Elevations at places inoculated indicate 

 the beginning of knots. 



April 25, 1908: Knots had formed but were quite small. They 

 had not developed as rapidly as those due to the regular daisy-knot 

 organism. On the rambler rose these same cultures produced no galls. 



Inoculations of March 21, 1909 (Brown). 



Three daisy plants of the Queen Alexandra variety were inoculated 

 by needle pricks with 5-day-old slant agar cultures from the rose gall. 

 Each plant was inoculated on from 3 to 5 shoots. Two plants were 

 held as checks. These plants were growing better than those pre- 

 viously mentioned. 



Result. — April 3, 1909: Small galls had formed at half of the inoc- 

 ulated places. The checks remained free. 



September 13, 1909: The galls grew slowly, as shown in the photo- 

 graph made on this date (PI. VII, fig. 2). 



ROSE ON ROSE. 



Inoculations op December 17, 1907. 



Twelve Killarney rosebushes were inoculated by needle pricks at 

 the crown with agar slant cultures 4 days old, the first subculture 

 from poured-plate colonies made December 10. Each inoculated 

 place was covered with a small piece of moist cotton. The crowns of 

 3 other rosebushes were punctured with a sterile needle for checks. 



Result. — January- 8, 1908: Small, white, knobbed prominences pro- 

 jected from the dark-colored root about a quarter of an inch on 2 of 



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