H. WORMALD 



47 



Experiment 2. 



On June 26, when the plums were about 2-5 cm. long and still quite 

 green, a series of inoculations, similar to that described under Experi- 

 ment 1, was carried out on two other trees, the only difference being a 

 modification in the manipulation when applying the conidia to the fruit. 

 The inoculations in this instance were made by placing the conidia- 

 bearing surface of a culture on steamed potato (the potato being cut up 

 into small pieces and used as in the experiments on plum flowers) on the 

 fruit; in the case of those plums inoculated through wounds the conidia 

 were brought in contact with the punctured skin and the needle then 

 inserted again in the wound to ensure contact of the conidia with the 

 cells surrounding the wound. 



As in the previous experiment no rot occurred except in those plums 

 which had been punctured and conidia placed in the wounds. The 

 modification of the former method of inoculation resulted in more 

 uniform results and each of the eight plums showed distinct evidence on 

 the second day after the treatment that a rot had set in; thus at each 

 of the nodes numbered 3 to 6 the inoculated plums showed a purple 

 discoloration extending for 2 mm, from the wound, while at nodes 7 to 10 

 the result was similar except that the colour of the affected tissues was 

 not so distinctly marked. 



The rapidity with which the rot extended through the infected plums 

 is shown in the accompanying tables. As in Experiment 1, plums at nodes 

 1, 2, 11 and 12 were inoculated by conidia being placed on the uninjured 

 skin, and again eight plums were punctured but not inoculated; these 

 are not shown in the table since they showed no signs of rot throughout 

 the experiment. 



Extent of the affected areas on the 2nd, 4th and 7th days after 

 inoculation made by placing conidia in punctures: the figures indicate 

 how far the discoloration had extended from the wound : 



July 3 

 Whole surface a dull purple brown and bearing pustules 

 Whole surface a dull purple brown and bearing pustules 

 Whole surface a dull purple brown and bearing pustules 

 As in No. 3 but the other plum of the pair is attached by 



a pad of hyphae 

 Whole surface discoloured and bearing pustules 

 Whole surface discoloured and bearing pustules 

 Whole surface discoloured and bearing pustules 

 As in No. 6 



