Introduction to Fungi, Third Edition

PYRONEMA (PYRONEMATACEAE)
415
Table 14.1. Families of the Pezizales which are commonly encountered in nature. Data from Kirk et al. (2001).
Families printed in bold are considered in more detail in this chapter.
Family Number of species Examples
Ascobolaceae (p.419) 118 Ascobolus, Saccobolus
Discinaceae 25 Gyromitra
Helvellaceae (p.423) 68 Helvella
Morchellaceae (p.427) 38 Morchella,Verpa
Pezizaceae (p.419) 160 Peziza
Pyronemataceae (p.415) 462 Aleuria,Otidea, Pyronema, Scutellinia
Rhizinaceae 2 Rhizina
Sarcoscyphaceae 36 Sarcoscypha
Sarcosomataceae 31 Galiella, Urnula
Terfeziaceae 15 Terfezia
Tuberaceae (p.423) 87 Tuber
quadrinucleate or multinucleate. They contain
one or several large lipid globules and may have
smooth or ornamented walls. Individual asci
may discharge their spores asynchronously, or
large numbers of asci may shoot off their spores
simultaneously. In this case, the spores may be
released in a visible cloud in a process known as
‘puffing’ (see Fig. 8.14). Buller (1934) investigated
this phenomenon in detail and reported that
ascospore puffing produces an audible hissing
sound. The asci of truffles, in contrast, are saclike
or globose, with no functional operculum,
and the spores are released passively.
The fruit bodies of some members of the
group are highly prized culinary delicacies, notably
truffles (Tuber spp.) and morels (Morchella
spp.). Gyromitra esculenta, the false morel, was
formerly also widely consumed but, following
a series of often fatal mushroom poisonings,
was eventually found to contain the heat-labile
toxin gyromitrin. This is readily converted
into hydrazine derivatives such as the rocket
fuel methylhydrazine, which are highly toxic
and carcinogenic (Bresinsky & Besl, 1990). Illustrations
of the ascomata of commonly occurring
Pezizales have been provided by Breitenbach
and Kränzlin (1984) and Dennis (1981). Selected
examples are presented on Plate 6.
Molecular phylogenetic analyses indicate
that the Pezizales are probably a primitive
group ancestral to other Euascomycete orders
(Fig. 8.17; Gargas & Taylor, 1995; Landvik
et al., 1997). This implies that apothecia are
an ancient type of ascoma, with cleistothecia
and perithecia representing later developments.
Whilst the Pezizales as a whole are monophyletic,
the arrangement into families within this order
is still tentative (Harrington et al., 1999). The more
important of the currently recognized families
are listed in Table 14.1. Since the morphological
and ecological features of pezizalean fungi
often transcend the family boundaries, we will
describe a few characteristic genera in more
detail by their biological features, merely
indicating their family assignment where
appropriate.
14.2 Pyronema (Pyronemataceae)
The apothecia of Pyronema develop on burnt
soil and on heat-sterilized composts in glasshouses.
There are two species, P. omphalodes (¼
P. confluens) and P. domesticum (Moore & Korf,
1963). In P. omphalodes the apothecia are confluent
and lack marginal hairs, whilst in
P. domesticum the apothecia are more discrete,
and surrounded by tapering hairs (Fig. 14.1a).
Pyronema domesticum forms sclerotia in culture
(Moore, 1962), whilst P. omphalodes does not.
In earlier studies the distinction between the
two species was sometimes not appreciated and