•202 Silver- Leaf Duease, Til 



The Slereum pwrpiirenni used for inoculation was obtained from a 

 silvered plum tree about two months before the experiments began and 

 was kept dry in the meantime. At the commencement of the inocula- 

 tions the sporophores gave a copious spore deposit after being moistened, 

 but as time went on the period required for the deposition of spores 

 increased, so it was considered advisable to use larger pieces of sporo- 

 phore in the inoculations in order to compensate for the possible diminu- 

 tion of vitality. All trees inoculated until April 'ifith became heavily 

 silvered during the summer, but after that date, silvering developed 

 only slightly or not at all in the inoculated branches, and in the latter 

 case there was no change the following year. 



This result is to be partly attributed to lessened vitality in the 

 fungus, but also perhaps in part to greater resistance of the host tluring 

 the period of active growth. 



A number of inoculations with sporophores of Sicrcinii pui-jiin-cinii 

 have been performed by placing the fungus in the bark only and not in 

 the wood. In other sporophore inoculations, the inoculating material 

 has been placed in a wound made into the wood. 



Of nine Victoria plum trees inoculated in this manner one winter 

 si.K became silvered the following spring, and examination of the 

 aft'ected branches showed that the fungus had spread extensively into 

 the wood from the bark. As was to be expected the progress of silvering 

 was at first slower than in trees inoculated directly in the wood. 



Another series of inoculations of young trees with portions of the 

 sporophores of Stereum purpureum may be mentioned. In March, 1918, 

 fifteen young Victoria trees were inoculated in this way and by July all 

 of these, with one exception, had become silvered, whereas none of the 

 controls became silvered. 



Sporophores of Stereum jjurpurenm from different sources — silvered 

 plum trees, dead beech trees, and willow stumps have all been used 

 for inoculation, but as the experiments published in 1913(2) show, there 

 is no difference in infectivity between Stereum purpureum. obtained 

 from sources associated with silver-leaf disease, and that obtained from 

 woody material which has not been connected with this affection. As 

 long as the sporophore is vigorous it almost invariably produces silver- 

 leaf by inoculation of a Victoria plum tree whatever the origin of the 

 fungus may be. 



During 1915 some material of Stereum fu,rpureum, from a silvered 

 cherry tree and from broom bushes respectively, was sent to one of us 

 from New Zealand by the kindness of Miss Piggott of Victoria College, 



