SOME FUNGI IN WOOD.
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in wood-rotting fungi the effect produced upon the wood is often
not sufficiently characteristic to enable an investigator to
identify the causal organism; a number of fungi, for example,
produce cubical brown rots. Without the presence of sporo-
phores, then, the identification of fungi in wood is often a difficult
matter and one for which the works of the systematist are of
little use. Several workers [e.g., 6, 12] have attempted to
surmount this difficulty, and a more or less standard technique
is now being used for this purpose; the characters on which the
investigator must rely are chiefly the vegetative characters of
the causal fungus—and vegetative characters are rarely as
reliable as those associated with the reproductive bodies, and the
6ymptoms which the fungus produces in the wood. It is largely
by comparison of these features with similar features of known
fungi that the identification of wood rots is possible.
To take an example: a mycologist receives a piece of rotten
wood and finds it necessary to identify the fungus responsible for
decay; the rot is of a type which he knows one of a number
of fungi may have produced, while there are no fruit-bodies
present by means of which an identification can be made. Part
of the specimen is detached and placed under conditions suitable
for fungus growth, since in this way it may be possible in time
to obtain sporophores. Next an attempt is made to grow the
fungus in the wood in culture under controlled conditions ;
usually this is not a difficult matter, for wood-destroying fungi
usually grow well on a jelly made of agar agar and malt extract ;
grown under sterile conditions on this or some other culture
medium a mass of mycelium will probably be obtained in a few
days. This it may be possible to match, in regard to form,
colour and texture or perhaps even physiological characters,
with some fungus from among the collection of standard cultures
of known fungi, which are kept for reference in certain institutions;
macroscopic characters may not be sufficient ; hyphae of the
unknown fungus must be compared carefully with those of known
species, under the microscope. The microscope will also be used
to study sections or fragments of the rotten wood for any
characteristic features, and for the fungal hyphae present therein.
Further it may be possible to obtain fruit-bodies of the fungus in
culture, but these will not always help, as such fruit-bodies are
frequently so abnormal as to be useless for the purpose of identi-