140 HEART-ROT CAUSED BY OTHER FUNGI 
by the mycelium. 1 have found similar conidia in larch 
wood, rotted by P. Schweiniteii, which has been allowed to 
lie about in the laboratory for some years, but have so far 
been unable to induce the conidia to germinate. I hope in the 
future to carry out further experiments with them to ascertain 
their relationship with the fungus that rotted the wood. 
Trametes Pini, (Thore) Fr. Thisis another wound parasite 
of the conifers which rots the heart-wood, and, to a limited 
extent, the sap-wood as well. According to Hartig it only 
gains admission to the tree through wounds caused by the 
fall of live branches. Unlike Polyporus sulphureus, it is by 
no means confined to trees growing in the open, but has 
proved destructive in plantations of forty years old and 
upwards. In woods of this age, owing to thinning, more 
space is given for the development of the crowns of individual 
trees, and consequently the branches reach a greater size. 
They are then more liable to be broken by wind or snow, 
especially on the more exposed edges of plantations, and it 
is in such exposed positions that the fungus is most pre- 
valent. Hartig (1878) has noted that the frequency of 
the disease on its four European hosts, Scots pine, larch, 
spruce, and silver fir, is in the order given, being greatest 
in the Scots pine and least on the silver fir, and that the 
frequency of broken branches follows the same order. 
Wounds left by the breaking off of small branches do not 
admit the fungus, as they are almost immediately pro- 
tected by a layer of turpentine and resin. But when a large 
branch breaks the broader core of heart-wood, which does 
not secrete these substances, is not so easily protected, and 
it is in the central portion of such a wound that the fungus 
first begins to grow. Thus inception of the disease generally 
occurs at some height above the ground. 
The disease affects the same genera of conifers in America 
as in Europe, with the addition of 7’suga, the hemlock 
spruce. It has also been reported as growing on willow 
(Stevens, 1913). In Britain, at any rate in the south of 
England, it is fortunately uncommon, so that it cannot be 
included as one of the more dangerous pests of larch cultiva- 
