H. WORMALD 45 



(2) Pairs of plums were selected in which the two of each pair were 

 in contact; one plum of each pair was inoculated by pricking with a 

 sterile needle (a single puncture being made in each case), piercing the 

 skin, and applying a drop of the water with conidia to the wound. 



(3) Controls: these plums were each wounded with a single puncture 

 but no conidia were placed on the wound. 



The fruiting spurs at which the inoculations were made were labelled 

 and numbered as follows : 



[ Treated as in method (1); both plums at each of the two nodes 



, i were inoculated without wounding by conidia in a drop of water 



[placed on the uninjured skin. 



3 V 



At each of these four nodes, one of each pair of plums was 



4 . 



[-inoculated as in method (2); the other plum of each pair was 



I left untreated in any way. 



c 1 Controls : both plums at each of the two nodes were pierced by 

 c j a single prick with a sterilized needle but not inoculated. 

 The above were all on one tree ; on the next tree in the row a similar 

 series of inoculations were made, i.e. : 



7 



Treated as nodes 3-6. 



8 



10 I 



11 1 



12 ( 



c) 



Treated as nodes 1 and 2. 



Controls treated as c, c on other tree. 



Thus in all eight plums were treated in each of the three ways. 



No rot occurred throughout the experiment on any of those inoculated 

 by placing conidia on the uninjured skin {i.e. plums at nodes 1, 2, 11 and 

 12), nor on those which had been punctured only. 



On those inoculated by placing drops of water containing conidia on 

 the punctures the results were as follows : 



June 23: no change to be detected in any of them except No. 6 on 

 which a discoloured^ area extended for 2 to 3 mm. round the wound. 



1 The rot was indicated externally by a dull purple brown discoloration of the skin 

 which was distinctly marked off from the green of the portion to which the rot had not 

 extended.- 



