66 CROWN-GALL OF PLANTS. 



PEACH ON PELARGONIUM. 



Inoculations op October 13, 1908 (Smith). 



Two vigorous-growing shoots on each of 2 plants of a common 

 red-flowered Pelargonium zonale were inoculated by needle pricks 

 from 3-day-old agar streak cultures of the peach organism after 

 it had been passed through red raspberry. 



Result. — November 16, 1908: Each of the 4 shoots bore a small 

 whitish corky-looking tumor where the needle entered, i. e., about 



1 sq. cm. was raised above the surface of the stem 3 mm. or more. 

 December 9, 1908: Two of the shoots were photographed and the 



material then fixed in Carnoy's solution for sections. 



January 18, 1909: The other 2 shoots were brought in and photo- 

 graphed (PL XIV). These shoots were still leafy and vigorous. 

 The tumors were more than an inch in diameter, but did not seem 

 to have done the plants any injury, i. e., the foliage above the gall 

 was not yellow nor dwarfed. 



PEACH ON PEACH. 



Inoculations of December 5, 1907 (Brown). 



Six young peach trees were inoculated with the peach-gall organism, 

 25 needle punctures being made in groups of 5 along the root, begin- 

 ning at the crown. Agar streak cultures 3 days old made directly 

 from the plate colonies were used. The inoculations were made in 

 the laboratory and the plants set out in pots in the greenhouse. 

 Two controls were held, the needle pricks being the same in number 

 and position. 



For comparison 6 peach trees were also inoculated with the daisy 

 organism, using agar cultures of the same age, and making the 

 punctures in the same way, in groups of 5 on the root, beginning at 

 the crown. 



Result. — January 8, 1908: Four of the 6 trees inoculated with the 

 peach knot organism had decided galls one-third to one-half inch 

 in diameter; and 4 of the 6 trees inoculated with the daisy organism 

 had galls about the same size. 



January 15: A photograph was made of the peach (PI. XI, fig. 1). 



February 14, 1908: All the trees inoculated with the peach gall 

 organism had galls, while galls had formed on only 4 of the 6 

 inoculated with the daisy organism. The galls were 1 to 2 inches 

 in diameter and alike on each tree. All the galls occurred at the 

 crown or just below it, in no case on the deeper inoculated roots, 

 nor were there any galls at other than the inoculated places. The 



2 check plants remained free from galls. 



213 



