EXPERIMENTS WITH THE DAISY OKGANISM. 39 



Most of the others have smaller galls, some of which have rotted away 

 except at the base. These galls are about 1 inch in diameter. No. 22 

 had gall about one-fourth inch in diameter. No. 25, gall not larger 

 than last spring. No. 26, gall about one-half inch in diameter (these 

 two are of the lot marked negative in April). No. 30 has two galls 

 about one-fourth inch in diameter. No. 34, scars of small galls. 

 No. 38 has no gall now visible — i. e., it has recovered. 



Inoculations of April 6, 1907 (Smith and Brown). 



Sixt3-nine peach trees were brought to the laboratory from the 

 Arlington Experimental Farm and washed carefully. All were free 

 from natural galls and were from a soil supposed to be uninfected. 

 They were labeled Nos. 90 to 158, inclusive. The first 21 (Nos. 90 

 to 110) were held as checks, being punctured on the roots with 20 

 needle punctures each, in groups of 5. The remaining 48 (Nos. Ill 

 to 158) were inoculated with agar streak cultures. Daisy plants were 

 inoculated with the same cultures for control. 



The roots of 24 trees were inoculated by Dr. Smith by means of 

 a needle, giving 15 pricks in 3 groups of 5 each (2 or 3 trees had more). 

 For this purpose he made use of ordinary brown moderately viscid 

 peptone beef agar cultures, 5 days old, and of white glycerin agar cul- 

 tures, 5 days old, also moderately viscid. 



Miss Brown inoculated 24 trees, giving 15 pricks in 3 groups of 5 

 each on the roots. 



Dr. Smith used 6 slant agar tubes (3 of each sort) as above. 

 Miss Brown used 6 slant agar tubes of the two sorts of agar (3 tubes 

 of each), each 48 hours old and not yet viscid. Work done in labora- 

 tory and very thoroughly. Plants set in hothouse. 



Result. — July 12, 1907: Dug to-day, brought in, w^ashed, and 

 examined all of the peach trees which were inoculated on April 6. 

 They fall into three groups, as follows: 



(1) Plants showing no tumors. 



(2) Plants on the roots of which small tumors have developed. 



(3) Plants on the roots of which larger tumors resembling the 

 ordinary crown-gall of the peach have developed. None of ''the 

 tumors are over one-half to three-fourths inch in diameter, i. e., they 

 are not full grown. 



Of the 13 uninfected plants (showing no tumors whatever) 5 were 

 inoculated from the older cultures, 8 from the younger. 



On the 17 plants showing small tumors the galls vary in size from 

 that of a small shot to a small pea. Six of these were inoculated 

 from the older cultures, and 11 from the younger. The tumors are 

 all on the main root, corresponding, so far as can be determined, to 



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