Introduction to Fungi, Third Edition

338 HYMENOASCOMYCETES: PYRENOMYCETES
Fig12.14 The course of events during eclosion of Hypoxylon fragiforme ascospores. (a,b) Dormant spores as seen in median (a) and
surface view (b), the latter showing the germ slits (arrowheads). (c e) Rupture of wall layer W1along a longitudinal seam, gaping of
germ fissure of ascospore, and escape of the spore from the perispore shell formed by wall layer W1.The sequence (c e) can be
observed some10 min after exposure of ascospores to the beech extract. It occurs abruptly, taking about 3 s. (f) Further distension
of valves composed of wall layers W2 W4, 30 min after addition of beech twig extract.The perispores are still visible as ghosts.
(g) Formation of a germ tube some 8 h after addition of beech twig extract. All images to same scale. Reprinted from Webster
and Weber (2004), with permission from Elsevier.
a concave layer lining the inner surface of the
wall in the basal region of the perithecium.
At the upper end of the perithecium a schizogenous
ostiole develops in the wall. It is lined
with periphyses, i.e. hyphae with free apices
which are attached at their bases to the inner
wall of the neck. At maturity, the perithecia may
protrude from the stroma and appear to be
seated on its surface. Perithecial development
of this type has been described for Nectria
(Strickmann & Chadefaud, 1961; Hanlin, 1971),
and for Hypocrea (Canham, 1969).
There is an exceptionally wide range of
anamorphs (Rossman, 2000; Seifert & Gams,
2001). In most cases conidiogenous cells are
phialides, and these may be terminal or lateral,
single or grouped in synnemata, sporodochia or,
more rarely, pycnidia. However, other
developmental types of conidia may occur and
in many species there are synanamorphs. The
conidia are generally light-coloured and
produced in slimy masses. The names of some
anamorph genera related to Hypocreales are
listed in Table 12.2. There is a tendency in
modern classification, with support of molecular
evidence, to link anamorph states with teleomorph
genera even if they have, as yet, no
proven connection from pure culture studies
(Rossman, 2000).
Many Hypocreales are saprotrophs active in
the decay of plant substrata above ground, in soil
or fresh water. Others are serious plant pathogens
(e.g. Nectria and Fusarium spp.) or mycoparasites,
especially of agaric, bolete or polypore
basidiocarps (e.g. Hypomyces, Apiocrea and
Hypocrea; Põldmaa, 2000) but also of cultivated