EXPERIMENTS WITH THE PEACH ORGANISM. 69 



Inoculations op January 23, 1908 (Brown). 



Five young Ben Davis apple trees, and 5 young Wealthy apple trees 

 were inoculated. Two Ben Davis and 4 Wealthy were held as con- 

 trols. 



A number of trees were discarded at the time of inoculation because 

 of the fibrous condition of the roots, and all were more or less sus- 

 picious because of the soil in which they had grown. The cultures 

 used for these inoculations were 2-day-old agar streaks, the fifth sub- 

 culture from plate colonies. From 15 to 25 needle pricks were made 

 on the main root of each plant on one side only, and the side inoculated 

 was mdicated by a notch on the stem. The trees were planted in 

 pots in the greenhouse. 



Result. — June 2, 1908: Two of the Wealthy apple trees had well- 

 developed knots on the inoculated side. Three were without knots. 

 Only 3 of the 5 inoculated Ben Davis trees could be found, and all 

 of these had knots. These knots were on the punctured side of 2 

 of the trees; but no positive conclusion can be dra\vn because of the 

 behavior of the controls. Of the 4 Wealthy used for checks 3 bore 

 knots and 1 was doubtful. Of the 2 Ben Davis 1 had a knot and 1 

 was free. 



As the controls bore knots, and in places where there were no 

 needle pricks, the conclusion was drawn that some of the trees at 

 least were infected in the field. 



Inoculations of March 11, 1908 (Smith). 



Three Wealthy apple trees were inoculated (1 in two places on a 

 top shoot and in one place on the base of a shoot at a considerable 

 distance above groimd; the other 2 in the top shoots only) with the 

 peach-gall organism from poured-plate colonies of March 4 — i. e., 

 derived from the interior of a crown gall on peach produced by a 

 pure-culture inoculation. 



Result. — June 1, 1908: The top shoot of plant 1 has given 2 well- 

 developed small tumors, the larger one round and about five-eighths 

 inch in diameter. The inoculation on the base of the shoot has 

 resulted in 4 distinct small tumors, each about 4 mm. high and 2 to 

 5 mm. broad. 



Plant 2 was inoculated in the top shoot in two places. In one 

 place it has given a tumor about 2 mm. high and about the same 

 diameter, and in the other place it has given 3 separate tumors, each 

 about 2 mm. high and 2 mm. in diameter. 



Plant 3 was inoculated at the base of two top shoots, each one of 

 which has given a group of small tumors 2 mm. in diameter and 2 

 mm. high. One of them has 4 of these tumors and the other has 3. 

 The development of these galls has been very slow. There are no 

 other tumors on the plant. 



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