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ON DISEASES OF PLUM TREES CAUSED 

 BY SOME SPECIES OF CYTOSPORA. 



By W. N. C. BELGBAVE, BA. 



(Research Scholar, University College, Nottingham, and formerly 

 Exhibitioner, St John's College, Cambridge.) 



Introduction. 



Within the last few years, an increasing number of plum trees in 

 the fruit plantations of Cambridgeshire have exhibited symptoms of a 

 "die-back" disease, followed by the formation of pycnidia, from which 

 red semi-gelatinous tendrils are exuded, these spore-masses belonging 

 to the genus Cytospora, the members of which are recognised as conidial 

 stages of various species of Valsa. 



This investigation was commenced at Cambridge, at the suggestion 

 of Mr F. T. Brooks, to whom I am much indebted for assistance. 

 The work was continued at Nottingham, and I desire to express my 

 thanks to Prof. J. W. Carr for permission to work in his laboratory. 



No serious damage to mature plum trees, caused by members of the 

 genus Valsa, has hitherto been recorded in England, though Massee (4) 

 has described Eutijpella prunastri (Sacc.) as attacking young plum 

 stocks. Aderhold (1) in Germany, and Wormald (5) in this country, 

 have described a strikingly similar disease of cherry trees caused by 

 Valsa (Cytospora) leucostoma. As all efforts to obtain mature asci have 

 failed, it is impossible to give the species of the fungus or fungi investi- 

 gated with any approach to certainty. 



Field observations and description op fructifications. 



The diseased trees examined belonged to three varieties, Victoria, 

 Prince of Wales, and Pond's Seedling. The trees attacked range from 

 those 4-5 years old, up to the very largest, and the attack usually proves 

 fatal. The first sign of attack is a withering of the leaves, usually 

 progressing from the top of the tree downwards. Next, areas of bark, 

 which may be on the main stem or a side branch, collapse and turn 



