CAUSE AND NATURE OF CROWN-GALL 29 



sixteen of the twenty seedlings which grew in the pots in which 

 the soil was inoculated with minced galls were diseased. Two 

 seedlings from one of these pots are shown in Fig. 9. Novem- 

 ber 8, 1899, eight seedlings in one of the check pots were cut 

 back to within two inches of the ground and incisions made at 

 the crown of each in order to ascertain if excessive pruning or 

 injury at the crown would cause the galls to develop. New 

 growth immediately began to develop and the wounds healed 

 over in the course of a few weeks, and on January 1, 1900, when 

 last examined, all were entirely free from the disease. 



SECOND SERIES OF EXPERIMENTS IN INOCULATING HEALTHY 

 SEEDLINGS BY MAKING INCISIONS THROUGH THE BARK 

 AND INSERTING BITS OF THE GALL. 



November 10, 1899, a large number of inoculations were made 

 by inserting bits of both old and young galls into incisions in 

 various seedlings. Ten healthy almond seedlings were cut back 

 and reset in the green-house. Previous to planting, incisions 

 were made at the crown and bits of old and partially decayed 

 galls placed therein. Ten almond seedlings were also treated 

 in a similar manner, with the exception that fresh, young galls 

 were used instead of old, dead ones. 



As all previous experiments were made on seedlings that had 

 been severely pruned and reset at the time of inoculation, five 

 almond seedlings, nnpruned and undisturbed in the soil, were 

 also at this time inoculated with bits of young gall. Ten peach, 

 ten apricot, twelve English walnut, ten grape, and five apple 

 seedlings were also inoculated with bits of young gall from the 

 almond. 



The ten almond seedlings that had been cut back and inocu- 

 lated with old galls on November 10, 1899, were examined 

 January 1, 1900. Developing galls were found on three speci- 

 mens at the places where the incisions were made. On this 

 date six diseased trees were found among the ten inoculated 

 with bits of young gall. The five plants inoculated without 

 cutting back or otherwise disturbing them more than necessary 

 in making the small incisions at the crown had all begun to de- 

 velop galls at the places where the incisions were made. In two 



