74 CEOWN-GALL OF PLANTS. 



PEACH ON PERSIAN WALNUT. 



Inoculations of October 13, 1908 (Smith). 



Two shoots of Juglans regia were inoculated by needle pricks with 

 agar streak cultures of Bacterium tumefaciens, plated by Miss Brown 

 from knots on red raspberry, which were produced by inoculating 

 with pure cultures plated out of peach crown-gall. 



These agar cultures were streaked on the 10th of October. The 

 two streaks are copious, somewhat raised up from the surface, smooth, 

 and wet-shining. Under the hand lens the lower part of the streak 

 has in certain hghts very fine irregularities on its surface, not notice- 

 able to the naked eye. The color of the shme is gray-white. The 

 spread away from the needle track is considerable. At the top it 

 extends to either side a distance of 2 mm. ; toward the base it extends 

 to either side of the needle track a distance of 5 mm. There is a 

 slight amount of water in the V, and this also is filled with the gray 

 sHme. The edge of the track is slightly undulatory. 



The walnut shoots were hard when inoculated, so no results were 

 anticipated. The plants were in a hothouse. 



Result. — No tumors developed. This negative result was attributed 

 to the fact above mentioned, i. e., that the shoots had ceased to 

 elongate and were hard when inoculated, so that the bacteria were 

 inserted into slow-growing tissues. This is the more likely because 

 inoculations made the same day on Pelargonium gave positive results. 



Inoculations of June 24, 1910 (Smith). 



Three green shoots of Juglans regia var. pendula were inoculated 

 in the softer terminal portion by needle pricks from a 2-day-old agar 

 streak culture of the crown-gall organism derived from the peach 

 (isolated in 1908). The shoots had reached nearly their definite 

 length and were, therefore, less satisfactory than they would have 

 been at the beginning of the month. 



Result. — August 15, 1910: No result. Possibly the organism is 

 losing virulence. 



PEACH ON TRADESCANTIA. 



Inoculations op May 7, 1909 (Brown). 



Six growing stems of Tradescantia were inoculated by needle 

 pricks with S-day-old agar cultures of the peach-gall organism (iso- 

 lation of 1908). Each stem was punctured 15 to 20 times. Two 

 stems were punctured with a sterile needle for checks. 



Result. — July 14, 1909: No trace of gall formation. 



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