Introduction to Fungi, Third Edition

STRUCTURE AND MORPHOGENESIS OF BASIDIOCARPS
517
Table 19.1. Distribution of fruit body morphotypes among the major clades of Homobasidiomycetes shown
in Fig. 19.2. From Hibbett and Thorn (2001).
Major clades
Hymenophore type
(A)
Agaricoid
(B)
Poroid
(C)
Hydnoid
(D)
Clavate
(E)
Resupinate
(F)
Epigeous
gasteroid
secotioid
(G)
Hypogeous
gasteroid
(1) Polyporoid þ þ þ þ þ þ
(2) Euagarics þ þ þ þ þ þ
(3) Boletoid þ þ þ þ þ þ
(4) Thelephoroid þ þ þ þ þ
(5) Russuloid þ þ þ þ þ þ þ
(6) Hymenochaetoid þ þ þ þ þ
(7) Cantharelloid þ þ þ þ
(8) Gomphoid phalloid þ þ þ þ þ þ
morphotypes shown in Fig. 19.1. This finding
is perhaps best explained by the assumption that
the first Homobasidiomycetes had a morphologically
simple fruit body form, probably the
flattened (resupinate) type, from which more
complex fruit bodies arose as numerous independent
evolutionary events (Hibbett & Binder,
2002). The class Gasteromycetes is an artificial
taxon, comprising gasteroid and secotioid fruit
body forms which have lost the capacity for
violent basidiospore discharge and have adopted
alternative mechanisms for spore dispersal
(see Fig. 19.2). Because of unifying biological
and morphological features, the gasteromycetes
are described separately in Chapter 20, where
we will refer to their affinity to the
Homobasidiomycete clades.
19.2 Structure and morphogenesis
of basidiocarps
The fleshy basidiocarps of many fungi belonging
to groups 2 5, 7 and 8 in Fig. 19.2 (‘agarics’)
differ from the tougher fruit bodies found in the
polyporoid and hymenochaetoid clades 1 and 6
(‘polypores’) in texture and construction. Agaric
basidiocarps are often umbrella-shaped, with a
centrally attached stalk (stipe) supporting the
cap (pileus) beneath which are the gills or tubes
lined by basidia. The polypores include bracket
fungi with basidiocarps which often bear pores
and are laterally attached to their substratum.
These fruit bodies are usually firmer in texture,
i.e. leathery, corky or woody. The differences in
texture reflect fundamental principles of
construction as shown by analysis of the
hyphae composing the basidiocarp. There are
also differences in development between agaricand
polypore-type fruit bodies.
19.2.1 Hyphal analysis
Corner (1932a,b, 1953) dissected the basidiocarp
tissues of various polypores and showed that
they were constructed of three distinctive types
of hyphae generative, binding and skeletal
(see below). Later work by Corner and others has
identified a further range of hyphal types
making up basidiocarps (see Pegler, 1996; Kirk
et al., 2001; Clémençon, 2004). This method of
hyphal analysis provides valuable criteria which
have greatly improved the taxonomy of the
genera of agaric- and polypore-type fungi.
However, it does not of itself provide the basis
for a higher-level ‘natural classification’ of
homobasidiomycetes.