SOME FUNGI IN WOOD.
43
Groom's [14] investigations led him to conclude that brown
oak was caused by a fungus with Penicillium-like conidiophores,
and he also found in the wood Melanogaster variegatus, var.
Broomeianus, one of the Gasteromycetes: we do not know how
far this is responsible for brown oak, but there are other fungi
as well which are known to produce a brownish discoloration:
thus a species of Penicillium may produce a yellowish stain on
hardwoods, especially in oak, and this fungus often occurs in the
early stages of kiln drying.
Before leaving the Polyporaceae we may turn to a considera-
tion of that group of fungi which, it is safe to say, is responsible
for the greatest amount of decayed timber in this country, the
dry rots. These are not a natural assemblage, they are not even
all members of the Polyporaceae; the term itself is confusing,
since it implies that this type of rot is associated with lack of
moisture, and this, as anyone will realise who has seen wood on
which Merulius lacrymans is growing, is far from true. While
dry rot is usually associated with Merulius lacrymans, Schum.,
the related Poria vaporaria Cooke, is also a causal fungus, and
Phellinus cryptarum Karst, has more recently been associated
with decay of oak timber. Apart from these members of the
Polyporaceae another common dry rot fungus is Coniophora
cerebella Pers., a member of the Thelephoraceae, while Groom.
[15] mentions as causal fungi Paxillus panuoides, Lenzites
saepiaria, and L. abietina. There is no need to give a long
account of dry rot, since it has been dealt with by numerous
authorities (e.g. [11, 15, 19, 27, 34]). The synonomy of
Merulius lacrymans is involved; the form, or perhaps species,
found in cellars and extremely rarely away from the haunts of
man is sometimes referred to as M. domesticus, while the wild
form is termed M. silvester. These two forms and others may
be merely races of M. lacrymans, although some authorities regard
them as distinct species. M. domesticus is a fungus very in-
tolerant to high temperatures, its optimum, as determined by
Cartwright and Findlay [7], being 23° C, while it does not grow
at all at 300 C. Its wild relative, M. silvester, while having the
same optimum temperature, will grow to some extent at 35° C.
M. domesticus is not found in the tropics, nor does it occur
in coal mines with an average temperature of over 25° C,
and Cartwright and Findlay suggest that the insolation in