FUNGI AND BEECH 233
elongated patches of black stromatal tissue in which the
perithecia are embedded. At another stage in the life
history of the same fungus pycnidia are formed as minute
and very inconspicuous flask-shaped structures embedded
in the bark. From each of these, however, there exudes
a coiled orange '' tendril'' of slimy spores perhaps half an
inch long. A large area of bark may bear thousands of
these tendrils, and in the mass they present a very striking
appearance.
It is not at all clear how far these fungi growing on bark
are living entirely at the expense of the bark and how far
they may also be attacking the wood. Careful work on
this problem is needed.
In the wood itself three major types of food are available
for lignicolous fungi. Firstly, in the sap-wood of a newly-
felled tree there is a considerable reserve of starch in the
medullary rays and the wood parenchyma. Secondly, and
most important of all, are the cellulose and hernicellulose,
which make up about 65 per cent of the dry weight of the
wood. Thirdly, there is the lignin, which accounts for
about 30 per cent of the dry weight.
When a beech is felled, fungi soon begin to colonise the
cut surface of the stump. Moulds, especially Alternaria
spp., are soon established. Sooner or later Bispora
monilioides usually makes its appearance as black, velvety
patches on the sapwood (Plate 11). The velvety "pile" is
the result of closely-set, erect, unbranched chains of black
two-celled spores. A month or so after felling, the conidial
fructifications of Coryne sarcoides almost always occur.
These are gelatinous, amethyst in colour, and occur crowded
together on the sapwood. Later on they develop into the
larger and paler apothecial stage. Other small fungi often
to be seen on the wood of the stump are Lasiosphaeria spp.,
with minute, black, hairy perithecia, sometimes crowded
together, and Dialonectria peziza, with tiny scattered
orange perithecia that collapse like deflated rubber balls
so that, superficially, they look more like apothecia than
perithecia.
It is generally considered that these small fungi are
living mainly on the starch of the sapwood, but the evidence
on this point is not abundant.