86 CEOWN-GALL OF PLANTS. 



Result. — June 1, 1908: Nos. 1-7, 9, 11, and 12 gave no tumors. 

 Plant 8, inoculated witli colony 8 in 2 })laces, yielded a tumor about 

 one-fourth inch in diameter. Plant 10, inoculated with colony 10 in 

 3 places, yielded a very slight tumor — a little round nodule about 2 

 mm. in diameter and 2 mm. in height. 



Remarks. — This experiment may be interpreted in at least four 

 ways: (1) That the plants were old and hard when inoculated and 

 thus resistant; (2) that the organism had lost virulence in the gall; 

 (3) that 10 of the 12 colonies were the wrong organism; (4) that the 

 daisy had become somewhat resistant as the result of previous inocu- 

 lations. Colony 8 is the only one that has given a tumor of any 

 considerable size. 



Inoculations of April 17, 1908 (Smith). 



Four daisy plants, Nos. 1 to 4, inclusive, were inoculated with the 

 hop organism from agar cultures 48 hours old. 

 Result. — June 1, 1908: No tumors. 



Inoculations of April 25, 1908 (Brown). 



Five more plants of the ordinary Paris daisy were inoculated with 

 slant agar cultures of the hop organism 2 days old. 



Result. — May 12, 1908: The same protuberances were formed as 

 in the first set of inoculated daisies, but no well-developed galls. 



Inoculations op May 9, 1910 (Brown). 



Eight terminal shoots on 3 large plants ready to blossom and 

 already inoculated on the lower part of the main stems with daisy 

 gall and bearing galls received punctures introducing the hop 

 organism from an agar culture several days old. 



Result. — June 23, 1910: Seven floral shoots failed to take (the main 

 stems below now bear large daisy galls). One vegetative shoot now 

 bears at the punctured spot 2 small smooth galls each about as large 

 as a pea and on directly opposite sides of the small branch. Six 

 inches below the main stem bears a large daisy gall. 



The reason for selecting dais}" plants already bearing tumors pro- 

 duced by the daisy organism was that all the numerous uninoculated 

 daisies of the same age were so much further advanced in flowering 

 than these inoculated ones that no soft tissues were available. 



Inoculations op November 12, 1910 (Smith). 



The preceding inoculations of hop on daisy having given such slight 

 results in comparison with hop on some other plants, daisies propa- 

 gated from stock never before used were inoculated with subcultures 

 3 days old from agar colonies (fresh isolation, California, 1910). 

 21 :{ 



