PROF. J. PERCIVAL ON “ STLVER-LEAF”’ DISEASR. 393 
I afterwards procured from nurserymen and fruit-growers in 
different parts of the South of England specimens of plum- and 
apricot-trees affected with “silver-leaf” disease. The plants 
were dug up completely, so as to obtain as much of the root- 
system as possible. Trees of various ages were obtained, some 
of them being maiden trees of one season’s growth only. In 
every case the root or underground portion of the stock was 
found to be diseased, the wood invariably showing internal 
discoloration when sawn across, although outside there was 
Fig. 5. 
Transverse section of root from a plum-tree affected with “ silver-leaf” disease. 
After being kept three days in a damp atmosphere the mycelium (@) developed, 
frequently no evidence of unhealthiness. Fungus-hyphe were 
always found in the wood near the junction between the living and 
dead portions, and in most cases a good growth of mycelium wis 
obtained when pieces of the diseased root were kept in a fairly 
damp atmosphere. . 
At first no spores or conidia were visible upon the mycelium, 
but after three or four months’ growth small sporophores of 
Stereum purpureum appeared upon the pieces of root. On several 
pieces of diseased root-stock which were dug up and exposed 
during the winter, Stereum purpureum also appeared. In one case 
only (Pl. 10) have I seen the fully developed fruiting-stage of the 
fungus on diseased trees ; such examples must be rare, or earlier 
investigators would have noticed them. 
. 9 
LINN, JOURN.—BOTANY, VOL, XXXV. ~@ 
