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THE ESSEX NATURALIST.
Fomes spp. One or two other species of this genus must be
noted briefly. F. ulmarius (Sow.) Fr., attacks elms, entering the
heartwood through wounds caused by broken branches, and at
first causing a brownish red discoloration of the heartwood;
later the infected wood disintegrates and the trunk thus becomes
hollow. F. robustus (Karsten) Bres., which is rare in this country,
produces a rot of which the incipient stages are brown turning to
yellowish as decay advances: normally confined to the sapwood,
it may attack the heartwood, but it is not very active, and decay
is slow, so that the fungus does not do a great deal of damage:
Cartwright and Findlay [8] suggest that it is sometimes confused
with F. igniarius. More common is Fomes ferruginosus (Schrad.)
Massee, which also attacks oak: Smith mentions the wood of
several other broad-leaved trees and also pine as susceptible
to attack. In oak it causes a white fibrous rot and is found
in fallen branches and on timber which is exposed to the
atmosphere. Its attacks are chiefly in the sapwood. Fomes
fomentarius (Linn.) Fr., which occurs on a number of broad-
leaved trees, is the cause of a white mottled rot in the
sapwood and heartwood; the mycelium is yellowish and occurs
in quantity in cracks in the decayed wood. Another white
mottled rot is due to Fomes (Ganoderma) applanatus Karst., and
is found in a number of broad-leaved and coniferous trees:
producing a butt rot, and sometimes a trunk rot in standing
timber, its attacks are said to occur in the sapwood as well as
the heartwood; felled timbers are also affected, and prepared
wood is likewise susceptible. This fungus is noted by Cartwright
and Findlay [S], who mention G. lucidum (Leyss) Karst., and
the less common G. resinaceum, Bourd., as also responsible for
white rots in oaks.
Polystictus versicolor (Linn.) Fr., is very destructive to hard-
woods in timber yards, and occurs on a variety of logs, producing
a white spongy rot which is more or less confined to the
sapwood.
Polystictus abietinus Cooke, is found on coniferous trunks,
and, like the last, frequently occurs in timber yards. It also
attacks the sapwood rather than the heartwood, and likewise
produces a white rot: in the final stages of decay the wood is
spongy, consisting of numerous small cavities of rot separated
by sound wood; owing to the position of these flake-like sound