36 THE ESSEX NATURALIST.
unable to enlarge the hole which was made by its tip. Sometimes
the boreholes are larger than the hyphae which occupy them, or
again they may be hour-glass shaped, which suggests that in this
instance the middle lamella has offered greater resistance to the
hyphal tip than the walls. Reference may be made to Hubert's
paper [19] for illustration of these types of penetration.
Rot in wood is usually characterised by two well marked
stages, although it must be emphasised that the disintegration
of the wood is a continuous process. The earliest macroscopic
sign of attack is frequently an abnormal discoloration of the
wood; this is often referred to as the incipient stage. The
second stage, referred to as the advanced or typical stage, marks
the period at which the cell walls are being broken down; it is.
now that the rot which we have come to regard as typical of a
fungus makes its appearance, i.e., the rot appears as a cubical
rot or a pocket rot and so on. Now of course the characteristic
rottenness appears—the wood may powder under slight pressure,
it may be broken with ease with a characteristic short fracture
(brashness), it gives out a dull sound when struck, and it may
emit a characteristic smell.
It may fairly be said that our knowledge of the wood-rotting
fungi is barely past its infancy. It may prove a tedious business
to associate a particular type of rot with a specific fungus, and
many more fungi will undoubtedly be associated with wood
destruction or discoloration as research proceeds. Although
there were earlier workers in the held, the title of father of forest
pathology must be given to Robert Hartig, whose classical re-
searches towards the latter end of the nineteenth century are
mostly summarised in his book, The Diseases of Trees. Since that
time wood pathology has occupied the attention of numerous
investigators, and has resulted in a fairly extensive literature,
both European and American. Among this may be noted
certain more extensive works such as those of Cartwright and
Findlay [8], Eades [9], Falck [10, 11], Hiley [18], Hubert [20].
We may now consider more specifically some of the members
of the British fungus flora which are responsible for the decay or
discoloration of wood. The list is not exhaustive, and no
attempt is made to describe the sporophores of the species under
consideration, since these are dealt with in the several systematic
treatises on the subject. Interest centres on the activities of the