Introduction to Fungi, Third Edition

576 HOMOBASIDIOMYCETES
independently in several unrelated basidiomycete
groups (Pine et al., 1999). For example,
Clavulina is now included in the cantharelloid
clade (p. 575). Corner (1950) has monographed
the clavarioid fungi and Petersen (1973) has
given keys to genera.
Clavaria and its allies
This is a large genus of pasture and woodland
fungi with cylindrical or club-shaped branched
or unbranched fructifications. The flesh of
Clavaria is made up of thin-walled hyphae
which lack clamp connections and may become
inflated and develop secondary septa. The hymenium
which covers the whole surface of the
fruit body usually consists of four-spored basidia
with or without basal clamps, bearing colourless
spores. A typical species is C. vermicularis
which fruits in grassland, forming tufts of
whitish, unbranched spindle-shaped basidiocarps.
Clavaria argillacea forms yellow clubshaped
fructifications on moors, heaths and
peat bogs. In North America fructifications are
consistently associated with ericaceous plants,
including cultivated blueberries (Vaccinium angustifolium
and V. myrtilloides), Azalea and Erica
(Englander & Hull, 1980). In Australia a similar
species is associated with cultivated Azalea
indica (Seviour et al., 1973). The close association
suggests a mycorrhizal relationship, and
although it has not been possible to synthesize
mycorrhiza by inoculating aseptically grown
ericaceous seedlings with mycelial cultures of
Clavaria, evidence in support of a mycorrhizal
partnership has been obtained by the demonstration
of a two-way transfer of radioactive carbon
and phosphorus between Clavaria and ericaceous
plants, and by immunofluorescence studies in
which hyphal coils were stained within root
epidermal cells with conjugated antibodies
raised against Clavaria basidiocarps (Mueller
et al., 1986). It is therefore likely that ericoid
mycorrhizae develop following root infection by
basidiomycetes as well as by ascomycetes such as
Hymenoscyphus ericae (see p. 442), and both groups
of fungi may infect the same root.
There are numerous other common representatives
of the Clavariaceae. Clavariadelphus pistillaris
(giant club) forms exceptionally large clubshaped
fruit bodies (7 30 2 6 cm) in beech
woods on chalk (see Fig. 19.1d). The construction
is monomitic, with clamps at the septa. As the
fruit body matures, the hymenium becomes
thicker by the development of further layers of
basidia. Some of the more richly branched fairy
clubs are placed in the genus Ramaria, distinguished
by tougher flesh and pink, yellow or
brown-coloured basidiospores, which are often
rough. A particularly striking example is
R. botrytis (Plate 10h). Most Ramaria spp. are
ectomycorrhizal (Nouhra et al., 2005); R. stricta is
exceptional in growing on rotten wood.