Introduction to Fungi, Third Edition

GASTEROMYCETES IN THE EUAGARICS CLADE
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20.3 Gasteromycetes in the
euagarics clade
The euagarics clade contains some 10 000 fungi
in 26 families (Hibbett & Thorn, 2001; Kirk et al.,
2001). Hymenia may be produced on the gills,
pores and ridges of mushrooms and on the
surface of coral-shaped fruit bodies, or basidia
may be enclosed in gasterocarps. Among the
gasteromycetes found within the euagarics,
the two most important families are the
Lycoperdaceae comprising puffballs and related
forms, and the Nidulariaceae (bird’s nest fungi).
20.3.1 Lycoperdaceae: puffballs
Puffballs such as Lycoperdon, Vascellum and
Calvatia form a phylogenetically well-defined
group which seems to be closely related to the
genus Macrolepiota both on the basis of DNA
sequence analyses (Krüger et al., 2001) and
because of similarities in the ontogeny and
architecture of rhizomorphs (Agerer, 2002). The
current family Lycoperdaceae contains 18 genera
and 158 species of gasteromycetes with epigeous
fruit bodies. The mature gasterocarp is thinwalled
and either forms an apical pore
(in Lycoperdon) or disintegrates from the apex
downwards (e.g. in Calvatia, Vascellum, Bovista).
Basidiospores are brown in colour and have
warty or spiny walls, with the distal part of the
basidial sterigma often remaining attached to
mature spores (Portman et al., 1997). Most species
are saprotrophic on soil and humus.
Lycoperdon
About 50 species are known, producing fruit
bodies which are pear-shaped or top-shaped.
Most species grow on the ground. Lycoperdon
pyriforme (Fig. 20.3) is unusual in growing directly
on old stumps, rotting wood and sawdust heaps.
It is not closely related to other Lycoperdon spp.
and is now called Morganella by some authors.
Gasterocarps of Lycoperdon spp. commonly arise
on mycelial cords. The individual cells of the
mycelium usually contain paired nuclei, but
clamp connections are absent (Dowding &
Bulmer, 1964). A longitudinal section of a
young gasterocarp of L. pyriforme (Figs. 20.3a,b)
shows that it is surrounded by a two-layered
peridium, but as the fruit body expands the
pseudoparenchymatous exoperidium may slough
off or crack into numerous scales or warts
(Fig. 20.2a) whilst the tougher endoperidium
made up of both thick-walled and thin-walled
hyphae remains unbroken, apart from a pore at
the apex of the fruit body. The tissue within the
peridium is differentiated into a non-sporing
region or sub-gleba at the base of the gasterocarp,
which extends as a columella into the
sporulating region (gleba) in the upper part of
the fruit body. The glebal tissue is sponge-like,
containing numerous small cavities, and in the
upper fertile part the cavities are lined by the
hymenium. The tissue separating the hymenial
chambers is made up of thick- and thin-walled
hyphae. The thin-walled hyphae break down as
the gasterocarp ripens, but the thick-walled
hyphae persist to form the capillitium threads
between which the spores are contained. The
basidia lining the cavities of the gleba are
rounded and bear one to four basidiospores
symmetrically arranged on sterigmata of varying
length (Fig. 20.3c). Young basidia are binucleate,
and nuclear fusion and meiosis occur in the
usual way. One nucleus migrates into each spore,
and if fewer than four spores are produced,
the spare nuclei degenerate in the basidium
(Dowding & Bulmer, 1964). The basidiospores are
not violently projected from the sterigmata. As
the glebal tissue breaks down and dries, the
spores are left as a brown dusty mass inside the
fruit body. An apical pore develops by controlled
lysis of the endoperidium (Fig. 20.2b). The thin
upper layer of the endoperidium is elastic and
acts as a bellows, and when rain drops impinge
on this layer, small clouds of spores are puffed
out (Gregory, 1949). Little is known of the mating
behaviour of Lycoperdon.
Calvatia
Gasterocarps about the size of a rugby football
are produced by Calvatia (Langermannia) gigantea
(Fig. 20.2c) growing on grassland and on
disturbed ground. There is no definite pore; the
peridium breaks away to expose a brown spore
mass. Buller (1909) estimated that the output of