Introduction to Fungi, Third Edition

SORDARIALES
317
The dark-coloured perithecia usually have an
ostiole lined by periphyses, but some genera are
astomous, i.e. they have fruit bodies lacking
ostioles, thus forming cleistothecia. Stromata are
not produced. The asci are unitunicate and thinwalled,
and the apical apparatus of the ascus is
in the form of a thickened annulus or apical
plate which does not stain blue with iodine. Freeended
paraphyses are often present but may
dissolve at ascus maturity. The ascospores are
black and sometimes surrounded by a mucilaginous
epispore, or they have mucilaginous
appendages. The spores are mostly unicellular
and germinate through a germ pore.
In the Chaetomiaceae, the ascomata (perithecia
or sometimes cleistothecia) are generally
clothed with thick-walled ornamented hairs. The
club-shaped asci are thin-walled and without
apical apparatus. If a hamathecium is formed, it
does not persist. The ascus wall dissolves and, in
perithecial forms, the ascospores are extruded as
a cirrhus. The ascospores are grey to brown in
colour, mostly unicellular and with a single
germ pore. Molecular data indicate a close
relationship between the Chaetomiaceae and
Sordariaceae (Huhndorf et al., 2004).
12.2.1 Sordaria (Sordariaceae)
Most species of Sordaria are cellulolytic.
Perithecia are common on the dung of herbivores
and occasionally on other substrata such as
seeds and plant remains, while a few species are
reported from soil. Guarro and von Arx (1987)
have given a key to 14 species, 5 of which are
coprophilous. Lundqvist (1972) has described and
illustrated Nordic species. Sordaria fimicola is
especially common on horse dung and has been
widely used in experiments on nutrition, the
physiology of fruiting, spore liberation and
genetics. It is homothallic, and perithecial development
occurs within 10 days on a wide range of
media. A longitudinal section of a perithecium
(Fig. 12.1) shows a basal tuft of asci at different
stages of development. The asci elongate in turn
so that only one ascus can occupy the ostiole at
a time. Because each spore is about 13 mm wide
and the diameter of the apical apparatus of the
Fig12.1 Sordaria fimicola. (a) L.S. perithecium.
(b) Ascus apex. (c) Ascospore showing mucilaginous
epispore. After Ingold (1971).