SOME FUNGI IN WOOD.
109
favourable for fungal growth; further, where bark is removed
from the logs, checking, which provides a means of entry for
fungal spores, will be more rapid than in winter.
Transport of timber from forest to mill may also favour
fungal infection; particularly is this so where timber is floated
out, and it will occasion little surprise, when the conditions
favouring fungal infection are borne in mind, that such wood
often suffers badly.
In structural timber adequate preventive measures do
seem to be more practicable. The covering of exposed timbers
with an impervious film, as by painting, or their impregnation
with a toxic substance, like creosote, is very effective; other
preservatives, consisting of inorganic salts, like zinc chloride,
sodium fluoride or copper sulphate, or certain organic substances,
have the advantage over creosote in being non-inflammable
and free from smell, and may be used for timbers in buildings.
The remarkable results obtained with creosote may be illustrated
by two instances noted by Fergusson [13]; he mentions a.
fence of creosoted pine which was erected at the Victoria Docks,
London, in 1854, and pulled down, although still serviceable, in
1920; he states also that the life of a softwood railway sleeper
in England is from 20-25 years, after which it becomes me-
chanically unsound, though showing little signs of decay. This
is a remarkable tribute to preservative methods, when one
considers that a railway sleeper is almost ideally situated from
the point of view of fungal attack.
A word on creosote treatment may not be out of place here.
The householder's method of applying the preservative with a.
brush is not very effective, although in my experience a good
deal better than nothing if the creosote is applied with a generous-
hand. But this treatment, at best, results in little more than a
surface film of preservative, and fungus spores, lodging in cracks,
may be able to germinate and infect the wood without difficulty.
The ideal method is to force the creosote in under pressure, and
to obtain penetration to a depth of about half an inch, while the
method often adopted on country estates is again quite effective.
This consists of placing the timber in cold creosote which is then
heated, the wood remaining in the liquid until it cools again;
the air in the wood elements expands as the temperature rises,
so that a good deal is forced out, while as the liquid cools, the