Introduction to Fungi, Third Edition

552 HOMOBASIDIOMYCETES
to form the stipe. Simultaneously, hyphae at the
apex of the bulb form horizontal outgrowths,
giving rise to the pileus. The development of the
hymenophore starts with the formation of small
alveoli on the lower surface of the pileus, near its
margin.
19.4.11 Tricholomataceae
This family has not yet been clearly separated
from related groups in recent phylogenetic
analyses. Genera currently placed here include
Tricholoma, Lepista, Clitocybe, Termitomyces and
Lyophyllum. A few Collybia spp. (C. tuberosa,
C. cirrhata, C. cookei) are also grouped here,
whereas most of the genus Collybia sensu lato
seems to belong to the Marasmiaceae (see p. 546).
It is probable that many other genera included
in the Tricholomataceae are also polyphyletic
(Moncalvo et al., 2000, 2002).
Clitocybe
This is a large genus with about 60 species in
Britain. The basidiocarps are funnel-shaped with
decurrent gills (Fig. 19.20a) and can be large, up
to 20 cm in diameter in C. geotropa. Clitocybe
nebularis may form fairy rings many metres in
diameter in deciduous and coniferous woods.
The fruit bodies of several species are edible and
those of C. odora have a fragrant, aniseed-like
flavour. Clitocybe spp. are non-mycorrhizal.
Lepista (50 spp.)
The basidiocarps of Lepista are generally known
as ‘blewits’ and include several good edible
species such as L. nuda and L. saeva. The gills
are attached to the stem in a sinuate manner,
i.e. with an S-shaped point of attachment
(see Fig. 19.8). Lepista is distinguished from
Tricholoma in having a pale pink spore print
(white in Tricholoma). Lepista spp. are nonmycorrhizal,
growing mainly among humus
and leaf litter.
Tricholoma (200 spp.)
This genus of mostly ectomycorrhizal species is
mainly North-temperate in distribution in woodlands
and pastures. The basidiocarps have sinuate
gills and produce a white spore-print.
The most important edible species is the matsutake
mushroom, T. matsutake, which is highly
valued, especially in the Far East. Unfortunately,
basidiocarps still have to be collected from
woodlands because all attempts at cultivating it
for commercial production have failed (see Wang
& Hall, 2004). However, Guerin-Languette et al.
(2005) have succeeded in infecting mature pine
roots with T. matsutake in the laboratory, and
this may have laid the foundations for an
inoculation protocol for forest trees in future.
An edible European species is St George’s mushroom
(T. gambosum or Calocybe gambosa) which
grows in pastures, often under trees, and fruits
in spring around St George’s Day (23 April).
Tricholoma sulphureum is a common woodland
species whose basidiocarps are readily recognized
by their sulphureous colour and unpleasant
smell.
19.4.12 Laccaria
The relatively small basidiocarps of Laccaria
(25 spp.) are known as ‘deceivers’ because of the
change of colour intensity of the cap surface
between wet (intensely coloured) and dry (pale)
conditions. Laccaria spp. are important ectomycorrhizal
associates of forest trees and are used
for artificial inoculation of trees to be planted
out into challenging situations. They are usually
among the early-stage colonizers of tree
roots, being replaced by others as the succession
proceeds (Last et al., 1983, 1987; Kropp & Mueller,
1999). Among the best known species are
L. laccata, growing with Pinus and a range of
other hosts, L. bicolor which grows with Abies,
Pseudotsuga, Pinus and Picea, and L. amethystina
(amethyst deceiver), an associate of oak (Quercus)
and beech (Fagus). All species of Laccaria have
edible basidiocarps. The relationships of Laccaria
are poorly resolved, and family assignment is
uncertain at present.
Bertaux et al. (2003) have reported the
presence of a bacterium (Paenibacillus sp.) within
the hyphae of L. bicolor. Bacterial cells were
visualized by fluorescence microscopy, and
the escape of these bacteria in liquid culture
conditions was shown to account for the sporadic
bacterial ‘contamination’ of fermenter