S. p. Wiltshire 



189 



spring, fissures arise which expose the tissues of the leaf base and readily 

 allow the canker fungus to enter. The host only slowly reacts against 

 the fungus which therefore quickly develops, in many cases surrounding 

 the stem and killing off the shoot above it. 



The view that the cracks resulting from the growth of the buds, afford 

 a means of entrance to the fungus in the spring, is also strengthened 

 by the observation, given above mth regard to the times of appearance 

 of bud infection. The Medaille d'Or x Kingston Black seedhngs are 



Text- fig. 2. Radial longitudinal section showing infection of the leaf base and the crack 

 through which the fungus first entered. There is no sign of phellogen formation and 

 the mycelium has penetrated deeply in the intercellular spaces. An infection of 

 Venturia inaequalis can be seen on the outside of the stem, x 25. m = mycelium ; 

 l.t. =leaf trace; fe = limit of infected region; 2'=pycnidia; a= Venturia inaequalis. 



naturally exceptionally late in bursting into leaf, but until this takes 

 place only very occasional infections can be found on the previous 

 season's growth. It appears that there is a definite correlation between 

 the appearance of canker and the swelling of the buds on the Kingston 

 Black X Medaille d'Or seedhngs and this fact points to the conclusion 

 that the growth cracks which accompany bud development allow the 

 entrance of the fungus. 



A point of interest which may be mentioned here is that further 

 infections of the canker fungus on the Kingston Black x Medaille d'Or 



