EXPERIMENTS WITH THE HOP ORGANISM. 89 



HOP ON ALMOND. 



Inoculations of April 16, 1909 (Brown). 



Three almond trees grown from the seed, and which were over a 

 year old, were inoculated on the stems and the crown with, agar 

 streak cultures 2 days old. No checks were held, as there were but 

 3 trees. 



Result. — May 6, 1909: No indication of galls forming. 



August 21, 1909: Galls formed on both crown and stems of 2 

 trees. The inoculations did not take on the third tree. This tree 

 was smaller, gnarled, and not in a good growing condition. 



November 19, 19C9: A photograph was made (PL XV, fig. 2). 



HOP ON PEONIA. 



Inoculations op May 6, 1909 (Smith and Brown). 



Three roots of Peonia officinalis were inoculated with the hop gall 

 organism. Checks were held. 



Result. — September 2, 1909: The plants were knocked out of the 

 pots and examined. No galls were found on those inoculated. We 

 were led to make these inoculations because Dr. Whetzel reported 

 root galls on peonia in New York. 



HOP ON SUGAR BEET. 

 Inoculations of April 17, 1908 (Smith). 



Six sugar beets were inoculated from agar subculture 48 hours old. 



Result. — May 18, 1908: Tumors have appeared and are three- 

 fourths inch or more in diameter (PI. XII, fig. 1). 



June 1, 1908: All of the inoculated sugar beets bear tumors. The 

 largest tumors are now 2 inches in diameter. 



Inoculations of March 7, 1910 (Brown). 



Five sugar beets were inoculated on the crowns by needle pricks 

 from 3- day-old agar cultures. 



Result. — April 20, 1910 : Galls are forming in the pricked parts. 



May 11, 1910: All contracted the disease and developed tumors 

 several inches in diameter (PI. XXI). Other beets in the same and 

 adjoining rows remained free from the disease. 



Remarks. — The hop organism used for the last inoculations on sugar 

 beet had been in the laboratory a long time, having been transferred 

 (without passage through plants) to fresh slant agar and bouillon 

 once a month for over 2 j^ears, i. e., about 26 times, to keep it alive, 

 and yet with all of these transfers it remained actively pathogenic. 



(See also checks, Hop on Daisy, Nov. 12, p. 86.) 



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