SOME FUNGI IN WOOD. 41
areas the rot frequently causes the wood to break up along the
annual rings, producing what is known as a ring rot.
Trametes Pini (Brot.) Fr., as a wood-destroying fungus, is
the best known species of the genus, and although uncommon in
Britain, it is common enough in parts of Europe, and in North
America, where Eades [9] says that it is easily the most wide-
spread wood rot. Numbers of conifers are attacked, the
fungus entering the heartwood through broken branches. The
incipient stages of the rot vary somewhat in different host
genera, but may be summed up as a discoloration of the heart-
wood, tending towards a reddish or greyish brown colour. In
the spruce (Picea excelsa) the incipient stage usually produces a
greyish colour which clearly marks off the sapwood from the
heartwood, although in a healthy tree there is no visible difference.
As decay advances small elongated pockets appear where the
wood substance has broken down and a white residue is left: a
white pocket rot is thus produced. These white pockets are
often numerous and give a honeycombed appearance to the
wood, while sometimes they coalesce in places, leaving plates
of less decayed wood between them and producing a ring rot.
Younger trees usually escape infection because of the flow of
turpentine, which seals the broken surface of small broken
branches, but in older trees where the fall of a large branch leads
to the exposure of the heartwood, this being dead is unable to
secrete resin, and consequently the wound surface remains
exposed.
Trametes suaveolens (Linn.) Fr., which occurs on willow, is a
wound parasite which produces a white mottled rot.
Daedalea quercina (Linn.) Fr., is another bracket fungus com-
mon in Europe and N. America, and occurring chiefly on stumps
and prepared timber: it is found on a number of broad-leaved
woods like beech and chestnut, but chiefly on oak. In oak the
sapwood is attacked more readily than the heartwood, although in
time the latter is affected. The decayed wood, which assumes a
reddish brown colour and breaks up into cubical masses, becomes
soft and easily crumbles, while mycelial sheets occur in the
cracks. Cartwright and Findlay [8] regard it as one of the most
important agents of decay in worked oak in this country; it
often occurs on oak exposed to the weather and may be found
in houses.