68 CROWN-GALL OF PLANTS. 



A greater number of the upper sets of pricks failed than of those 

 farther down on the root. (By ''upper" is meant near the crown.) 



The surface of selected washed galls was sterilized three minutes 

 in mercuric chlorid water (1:1,000), portions from their interior 

 removed with sterile knives, mashed in beef bouillon, and plates 

 poured — one set by Miss Florence Hedges and another by Miss 

 Lucia McCulloch. 



March 7, 1908 : Each set of plates yielded many colonies of the right 



organism. 



Inoculations of March 24, 1908 (Brown). 



On February 29 an organism was plated out of the interior of one 

 of the galls (peach strain) obtained by the inoculations of December 

 5, 1907, and on March 24 inoculations were made in the greenhouse 

 on 10 healthy peach trees to determine whether or not this was the 

 crown-gall organism, i. e., the same schizomycete as that inserted. 

 Four-day-old agar streak cultures were used — the first subculture 

 from the poured-plate colonies. The inoculations were made at the 

 crown by means of needle pricks. The trees had been moved in 

 recently from a cold frame. Five of the trees had developed foliage; 

 5 others were just beginning to show foliage. Four checks were held, 

 punctures being made in the same way as on the inoculated plants. 



Result. — Jmie 2, 1908: Galls 1 inch to 2h inches in diameter were 

 found on 5 of the inoculated trees. On one other tree a gall had 

 formed and then rotted off. Three trees showed no indication of 

 galls, but the roots were abnormal, i. e., there were many fibrous 

 roots. The tenth inoculated tree was missing. The 4 check plants 

 remained free from galls. On the inoculated plants the galls were 

 restricted to the inoculated parts. 



August 10: Photograph made. 



All further inoculations with the peach gall organism so far as made 

 by Miss Brown were with this strain plated from one of the galls 

 produced by inoculation. 



PEACH ON APPLE. 



Inoculations of January 16, 1908 (Brown). 



Six young apple trees from the Arlington Experimental Farm were 

 inoculated with agar streak cultures 1 day old, the fourth subculture. 

 Fifteen needle pricks were made on the main root of each plant. 

 Four check plants were held. The inoculations were made in the 

 laboratory and the trees set out in pots in the greenhouse. The 

 trees (variety Wealthy) were not in good condition and were dormant. 

 It is important to keep these facts in mind. 



i?eswZ^.— April 7, 1908: No trace of a knot on any tree. 



213 



