86 



PLANT DISEASES 



When the flowers are formed, the mycelium of the fungus 

 travels from the interior of the branch bearing the flower 

 into the young ovary, the result of which is that instead 

 of developing into a normal plum, it grows, under irritating 

 influence of the parasite, into a deformed, useless structure 



Fig. 12. Exoascus pruni. i, portion of a branch bearing three 

 diseased plums ; 2, section through a diseased plum. 



of variable form and size, shaped like a finger or a club, often 

 more or less curved and flattened, and having the surface 

 irregularly wrinkled or warted, at first of a yellowish colour, 

 afterwards becoming tinged with dingy red. The entire 

 structure is dry, and not at all fleshy or succulent like a 



