F. T. Brooks and M. A. Bailey 193 



foliage. In addition to the shoots arising from the stumps, one sucker 

 arising some distance away from them was silvered. Affected leaves 

 were examined during September and fresh sections showed 20-50 per 

 cent, of the palisade cells with disorganising chloroplasts, the sections 

 as usual showing a marked tendency to fall asunder. It is not known 

 how long these leaves had been silvered. 



The only other record of silver-leaf in poplars as far as can be 

 ascertained occurs in the report of the Scientific Committee of the 

 Royal Horticultural Society for 1913, when one or two of a number of 

 leaves of a poplar attacked by Ascomyces (Tafhrina) aureus submitted 

 to the Committee were said " to show the silvery appearance character- 

 istic of the attack of Stereum furpureum as seen in plums." 



As regards other plants referred to in the previous paper (2), in 

 which silvering was associated with Stereum furfureum, it may be stated 

 that in hundreds of plum trees, especially Victorias, seen in different 

 parts of the countrv, the association of this fungus with dying silvered 

 branches has been invariable. The character of the soil appears to have 

 little influence on the incidence of the disease in plums, which seejiis to 

 be as conmion on soils amply provided with lime as it is where this 

 constituent is less abundant. In addition to Victoria, the variety Czar 

 is also very susceptible to silver-leaf in some districts, but other varieties, 

 e.g. Monarch, Early Rivers, Pond's Seedling, and Pershore are only 

 occasionally attacked. The relative immunity of the large mature 

 areas of the last-named variety in the Evesham district is very striking. 

 A belief prevails there that the variety Victoria worked on the Pershore 

 stock instead of on other stocks generally used, e.g. Brampton, is thereby 

 rendered relatively immune from silver-leaf disease. There is, however, 

 no definite evidence yet that this belief is well founded and certain 

 inoculation experiments described below do not support it. Occasionally 

 Stereum hirsutum as well as Stereum purjjiireum is seen on silvered plum 

 trees, but as described under the heading of inoculation experiments, 

 the former cannot be considered a cause of silver-leaf. 



With silvered apple trees, the presence of Stereum furfureum is by 

 no means so constant as in plums except possibly in regrafted trees. 



A silvered cherry tree near Cambridge came under observation in 

 1913, several of the diseased branches containing discoloured wood, but 

 it is not known whether Stereum purpnreum subsequently developed 

 upon it. Another silvered cherry tree was seen in the North of England 

 in 1916. As will be shown later, silvering has been induced in old cherry 

 trees b}^ inoculation with Stereum. purpureum. Some cherry trees about 



