206 Silver- Leaf Disease, III 



to determine with which ol these the greatest amount of diseased wood 

 was associated. 



Portions of the affected branches were cut up and placed on moist 

 sand and fructifications of Sfereum purpnreum developed on several of 

 them within two months. During the summer of 1915, Stereum purpur- 

 eum developed in abundance on the cut end of the stump of this tree 

 remaining in the ground and nearly all the shoots arising from it were 

 silvered. 



(2) \farners King. Fifteen scions were inserted in various ways 

 and, of these, ten developed normally during 1913, the other five dying. 

 During 1914 six of these living scions became silvered, the foliage of 

 the others remaining normal. Portions of the tree were cut down in 

 March, 1915, and the distribution of discoloured wood investigated, 

 with the same result as in the tree just described. Stereum piirpureuin 

 developed on some of these portions after being kept on moist sand for 

 two months. 



(3) Codlin. Eleven scions of Bramley Seedling were inserted, of 

 which six developed normally during 1913 and 1914, the others dying. 

 During 1915 the foliage of five of the scions became silvered. 



(4) French Crab. Nineteen scions of Bramley Seedling were inserted 

 of which thirteen developed normally during 1913, 1914, and 1915, the 

 others dying. 



In these regrafted trees the evidence points to Stereum purpureum 

 as the cause of silvering, though it is by no means certain that this 

 fungus is always the cause of silvering in regrafted apple trees. 



It is obvious that, in regrafting operations, there is considerable 

 opportunity for the entrance of a wound parasite like Stereum pur- 

 pureum, but regrafted apple trees which become silvered often rapidly 

 grow out of the malady. 



In the trees referred to above, the character of the silvered leaves 

 was the same as in plum leaves typically silvered. Thus the upper 

 epidermis could be readily stripped off and the mesophyll cells had a 

 tendency to fall asunder when sections were cut. 



{(■) Inoculation experiments with other plants. 



Other kinds of woody plants have been inoculated with Stereum 

 purpureum to see whether silver-leaf could be induced in them by this 

 means. The following have been inoculated with success by inserting 

 into the stem small pieces of sporophores: cherry (old trees), red currant 

 (fructifications of Stereum purpureum subsequently developed on one 



