194 Silver-Leaf Disease, III 



ten years old which were cut back in 1915, showed silvered shoots 

 arising near the unprotected extremities during 1916. Examination 

 showed that the portions bearing the silvered shoots contained much 

 discoloured wood whereas in parts similarly cut back and bearing 

 healthy branches there was very little discolouration of the tissues. 



Several additional silvered red currant bushes have been seen on 

 which Slereum purpureum developed. 



Silver-leaf is of common occurrence in the Portugal laurel and it has 

 often been seen in connection with dying back of the branches. Other 

 observers have seen Slereum purpureum in association with the disease 

 on these plants. 



On the other hand, examples of trees killed by Stereum purpureum 

 with which the phenomenon of silvering was not associated, have been 

 seen. Since 1913, when brief reference (2) was made to this possibility, 

 certain birch and plane trees grownng in gardens, after being severely 

 cut back, have been rapidly killed hv this fungus without silvering 

 of the leaves being evident. 



In 1913 (2) it was pointed out that several examples of silvered 

 foliage had been seen with which there was no connection with Slereum 

 purpureum. 



Since that year numerous other examples of silvered foliage have 

 come under observation which could not have been induced by Slereum. 

 purpureum, and with which there could have been no connection. 



In 1913 (2) the silvering of certain batches of seedling plums was 

 described, and it was pointed out that, though this affection was strictly 

 comparable with the silvering of adult trees, it was certainly not attribu- 

 table to Stereum purpureuu) as no fungus mycelium was found in the 

 tissues. 



Since then several other lots of seedling plums and other seedling 

 plants have been examined and many of them have shown silvering. 

 The affection, if it is really an affection in these cases, is capricious in 

 occurrence. Of batches of seeds treated apparently in the same manner, 

 some may give rise to silvered seedlings while others develop normally. 



The subsequent history of the silvered plum seedlings raised by 

 Mr W. 0. Backhouse and described in 1913 (2) will first be given. 

 Before planting out in the open during May, 1912, several of these 

 silvered sepdlings were examined microscopically and although sections 

 of the leaves showed the usual tendency to fall asunder, no trace of 

 fungus attack could be found in stem. leaf, or root. During the summer 

 and earlv autumn of 1912, the condition of these silvered seedlings 



