90 CEOWN-GALL OF PLANTS. 



HOP ON HOP. 



On October 23, 1907, a hop root from California with a good-sized 

 gall was brought into the laboratory by Dr. W. W. Stockberger for 

 examination. Plates were poured from this gall and the gall organ- 

 ism obtained. 



Inoculations of November 21, 1907 (Brown). 



Only 4 hop plants could be obtained, and these were inoculated by 

 needle pricks at the crown with cultures 2 days old. 



Result. — January 15, 1908: The plants had made almost no growth, 

 but 3 of them had small galls at the inoculated places. 



Isolation of organisms. — On January 28, 1908, some more hop roots 

 with irretrular sails 4 to 6 inches in diameter were received from Cali- 

 forniatlirough Doctor Stockberger. Parts of these galls were blackened 

 and decayed; some swarmed with nematodes and some had small 

 white nodules of new gall tissue on the margin of the old blackened 

 gall tissue. These young portions were used for pouring agar plates, 

 and 7 days later the gall colonies appeared on the plates. 



Inoculations of June 10, 1908 (Brown). 



Eight seedling hop plants grown in the greenhouse were inoculated 

 at the crown with slant agar cultures 4 days old. Four other seed- 

 lings were punctured with a sterile needle for checks. 



Result. — July 20, 1908: Galls 1 to 2 inches in diameter had formed 

 on all the inoculated plants. The checks bore no galls. 



CHESTNUT ON DAISY. 



Inoculations of November 13, 1908 (Brown). 



Four shoots of a daisy plant w^ere punctured and a little of a pure 

 culture introduced on the point of the needle (same cultures used on 

 sugar beets). 



Result. — December 2, 1908: Tlie inoculations showed only as a 

 slight swelling. 



December 19: Perceptible galls are now visible on the daisy at the 

 points of inoculation. 



March 13, 1909: The galls are now 1 to H inches in diameter 

 (PI. XVI, fig. 1). They grew more slowly than any gall heretofore 

 observed except perhaps peach on daisy (inoculations of February 3, 

 1908) and some of peach on apple (inoculations of March 11, 1908). 



May 3, 1909: The galls ai-e still growing, nearly 2 inches in diameter, 

 and quite tough. 

 21. -J 



