38 CKOWN-GALL OF PLANTS. 



DAISY ON PEACH." 



Inoculations of March 11, 1907 (Smith and Townsend). 



Received 27 one-year-old peach trees from Arlington Experimental 

 Farm; washed the roots very thoroughly in running tap water for 

 half an hour, with hand rubbing, then rinsed thoroughly twice in 

 distilled water. All were free from crown-gall and otherwise sound. 



Held 9 as check plants, making 20 needle pricks in the crown of 

 each one, i. e., in the bleached part of the stem just below the earth 

 surface. Divided the other 18 into two groups. One group was 

 inoculated with a quite viscid 5-day-old culture on ordinary slant 

 agar. The other 9 were inoculated with a 6-day-old culture on 

 slant glycerin agar. Each one of the inoculated plants received 10 

 pricks (5 on one side and 5 on the other), mostly in the white tis- 

 sues of the crown of the plant, but a few lower down in the taproot. 

 They were then taken to the hothouse and planted in good earth in 

 10-inch pots. Young daisy plants were pricked for control (1 from 

 each culture). 



One culture was also pricked into a young slioot of olive with 

 negative results, as already recorded (p. 33). 



Result. — March 29, 1907 : Nos. 33 and 37 were dug and photographed 

 (at end of 18 days). 



April 3, 1907: The roots of all the trees were examined, and 15 out 

 of the IS were found with tumors where inoculated, the largest being 

 about one-fourth inch across. Five of the roots had 2 tumors each. 

 All inoculated with the younger culture, with one exception (No. 32, 

 a dying tree), developed tumors. Of the other 9, 7 showed tumors. 

 What appeared to be incipient tumors were also found on the roots 

 of the 2 trees counted as negative, so that probably all of the inocu- 

 lated plants, except the dying one, would in the end have shown 

 well developed tumors. On these 18 trees there were no tumors 

 when inoculated, nor afterwards, except where the infected needle 

 entered. 



April 5, 1907: The 9 check plants punctured on March 11 as 

 controls for the inoculations were dug and examined. No tumors 

 were found on the roots of any of them. They were repotted and 

 returned to the house. The daisy controls had tumors. 



January 29, 1908: After their examination on April 3, the inocu- 

 lated trees were repotted but made very little growth for a number of 

 weeks. This setback we now know to be very injurious to the 

 development of galls on roots. To-day the trees were dug to be 

 thrown away, and the following conditions were observed: 



On No. 36 a large gall just underground, the same being about 

 2\ inches in diameter and nearly encircling the root (PI. VI, fig. 1). 



o See also daisy under " Peach on Peach" (p. 66), check inoculations of December 5, 1907. 

 213 



