H. WORMALD 43 



8th day: many of the flowers were withered, the calyx lobes being 

 brown and withered, and the pedicels brown and longitudinally sulcate 

 to the point of insertion on the receptacle of the umbel {i.e. the tip of 

 the flowering spur); in a few the tissues of the spur itself were invaded 

 as shown by the fact that the discoloration had reached the base of the 

 pedicel of one flower of the pair and was extending ujnvards from the 

 base of the pedicel of the second flower. 



At this stage the rest of the flowers on the tree showed generally 

 only a normal discoloration of the stigmas ; in a few it had extended for 

 a short distance down the style. Two umbels however showed a browning 

 of style and ovary with the discoloration extending to the pedicels, and 

 it was evident that these had become infected also, the infection probably 

 having arisen by conidia carried by bees from artificially inoculated 

 flowers. There were no flowers quite withered except among those on 

 which conidia had been placed at the beginning of the experiment. 



10th day: the disease had extended further into the flowers and 

 pedicels and on some of them Monilia pustules with conidia were present. 

 In three cases the fungus had advanced into the tissues of the spurs and 

 by cutting off supplies to the leaves round the bases of the flowers, pro- 

 duced a wilting of the leaves. 



12th day: the leaves of other spurs were also wilting and examination 

 showed that the discoloration began at the base of the petiole, thus show- 

 ing that the disease was invading the leaves from the spur. 



With regard to the flowering spurs which had not been artificially 

 inoculated (some hundreds in number) on the same tree, only two at this 

 time bore withered flowers and leaves and one other had dead flowers. 

 These three spurs were all in the neighbourhood of inoculated umbels, 

 being from 9 to 15 inches from the nearest flowers inoculated from the 

 culture; their proximity to the artificially inoculated flowers suggests 

 that bees had carried conidia from the stigmas of the latter to those of 

 neighbouring flowers. 



5 weeks : all the inoculated flowers had been dead for some time ; at 

 some of the nodes the disease had not only killed the flowering spur but 

 had reached the branch and girdled it (so causing the death of the distal 

 portion) or had produced a canker partly girdling the branch. In some 

 instances gum had issued from the bases of the infected spurs. 



It is evident therefore that the strain of Monilia cinerea used in this 

 experiment, a strain obtained from a twig affected with the " Wither 

 Tip " disease readily infects plum flowers, invades the spurs, and is able 

 to produce cankers on the branches. 



