1. An introductory survey is made of the distribution, uses, synonyms and ststematic position of
Polyporus betulinus (Bull) Fries.
2. Parasitism is discussed. Negative results have
been obtained from infection experiments; but field
observations force the writer to the opinion that
the fungus is a parasite.
3. From observations in Nature and in culture the
type of breakdown produced in the attacked wood is
classified as a red-brown cubical rot. The microscopic characters are listed following Hubert's
method. The stages in decay are illustrated.
4. A brief survey of the enzyme content is made,
following Buller's methods. The fungus is shown
to contain a variety of ferments capable of attacking the woody tissues of the birch. It appears to
belong to both the lignin-destroying and the
cellulose-destroying groups of wood-attacking fungi.
5. The culture characters of the mycelium are investigated and the fungus classified according to
6. Black lines are formed in culture. These are
related by position with bulbils (sclerotia). It
is suggested that here, as elsewhere, both are resting stages.
7. Sporophores are described in Nature and from
culture. The hymenium consists of pores lined by
basidia and sparingly interspersed with cystidia.
These latter appear to be modified fibre hyphae.
The sequence of nuclear phenomena in the basidium
is traced. The period of spore discharge is determined for the species and for individual sporophores.
8. From an examination of the structure of sporophores,
bulbils and zone lines it is suggested that all
three are constructed on the same fundamental plan.
9. The life history of the fungus has been carried
through from spore to spore in culture, in a space
of three months.
10. Monospore cultures were obtained. The fungus is
heterothallic. The spores were shown to fall into
two groups by pairing 12 monospore colonies in
every possible way. Monosporous mycelia show
single nuclei and no clamp connections. The normal hyphae contain paired nuclei and bear clamp
11. A bibliography of 75 titles is appended.