HEART-ROT CAUSED BY OTHER FUNGI 137 
alder, willow, poplar, walnut, pear, and larch (Hartig, 
1894); in America it is recorded on a similar range of 
broad-leaved trees, but appears to be much more general 
on conifers, and is reported as a parasite on pine, spruce, 
hemlock spruce, &c. (Schrenk, 1900 ; Atkinson, 1901). Itis 
not. uncommon in England, where it is most frequent on 
the oak, but also attacks the larch, yew, and other trees. 
Infection generally takes place through wounds left by the 
pruning or breaking of large branches, so that single trees 
grown in the open are much more liable to attack than 
plantations in which side branches are killed before they 
attain sufficiently large size. Branches which die naturally 
through being shaded by the crown are less likely to intro- 
duce the fungus, but Atkinson observed one case in the 
American white oak in which the fungus had apparently 
entered through a dead leader which had become included 
in the gradually thickening trunk. This, however, is excep- 
tional, and the occurrence of the disease in larch woods 
may be regarded as evidence of an open canopy which has 
allowed undue development of side branches. In parks, 
where such development is normal, the snow-break, or 
wind-break, of large branches will furnish ‘ infection courts ’ 
for the fungus, unless the timely treatment of such wounds 
is resorted to. 
The fungus makes large annual bracket-shaped fructifica- 
tions which are usually imbricated, i.e. a number grow 
together, one above another, and are generally found on 
wound surfaces between May and September. They are 
easily recognized from all other polypores by their colour, 
being bright orange above and sulphur yellow below. The 
soft flesh of young fructifications is full of a clear yellow 
fluid, and the upper surface particularly is very moist and 
turns brown when bruised. This surface is somewhat hairy 
and when mature becomes hard and brittle. Drops of water 
containing melezitose (Schrenk) collect on the lower side, 
which is marked by very fine pores. The whole fructifica- 
tion develops very quickly, and soon after maturity is 
destroyed by grubs. 
