Introduction to Fungi, Third Edition

554 HOMOBASIDIOMYCETES
phylogenetic analyses (Moncalvo et al., 2002).
Two groups of Psilocybe fall outside the core of
the Strophariaceae, with the hallucinogenic
species clustering separately from other
Psilocybe spp.
Stropharia
Species of Stropharia fruit on soil, dung or wood.
The developing gills are protected by a membranous
veil which may persist as a solid annulus or
a loose weft of fibrils. The spores are purplishbrown
to black. Stropharia semiglobata, extremely
common on several kinds of herbivore dung, has
a viscid, yellowish, hemispherical cap and a ring
of dark fibrils on the stem (Fig. 19.20b). Stropharia
aeruginosa (verdigris agaric) has an attractive
bluish-green viscid cap flecked with white
scales and grows in woodland while S. aurantiaca,
with bright orange caps, fruits on sawdust and
on wood chippings.
Psilocybe (c. 300 spp.)
The basidiocarps of Psilocybe (Fig. 19.20c) are
generally small and campanulate (bell-shaped),
with attached gills and purple-brown spores.
Some species have a fibrillose veil whilst others
have a distinct annulus. The genus includes
several species whose basidiocarps are hallucinogenic
and are used as recreational drugs. Psilocybe
mexicana (sacred mushroom, teonanácatl) has
been used for centuries by Mexican Indians in
religious ceremonies (Heim & Wasson, 1958),
and P. cubensis (golden top or giggle mushroom)
is cultivated to obtain hallucinogenic basidiocarps.
In Europe, P. semilanceata (magic mushroom,
liberty cap) fruits in late summer and
autumn on the ground in sheep pasture and
well-manured grassland. It is saprotrophic, its
mycelium being associated with decaying grass
roots. Fruit bodies are picked and dried,
although their sale is illegal in many European
countries. The main hallucinogens of Psilocybe
are the alkaloids psilocybin and psilocin
(Figs. 19.15f,g), which are N-methylated tryptamines.
They operate on serotonergic systems of
the brain and are similar in their effects to
mescaline and LSD (Lincoff & Mitchel, 1977;
Bresinsky & Besl, 1990). Psilocin is less stable
than psilocybin, and when oxidized shows a blue
discoloration. This may be the reason why
the flesh of many of the hallucinogenic Psilocybe
spp. turns blue when bruised or broken.
A readable account of the discovery of LSD
and the elucidation of hallucinogenic principles
in magic mushrooms has been written by
the discoverer of both, Albert Hofmann. English
translations of the original German text
(Hofmann, 1979) are readily available.
Hypholoma
The best-known species are H. fasciculare (sulphur
tuft) and H. sublateritium (Fig. 19.20d), both
growing on wood. They are sometimes classified
in the genus Naematoloma. Hypholoma fasciculare
is very common, forming clusters of yellow
basidiocarps on many kinds of deciduous and
coniferous tree stumps, whilst H. sublateritium
fruits on deciduous tree stumps and has brickred
caps. There is a cottony veil on the stem and
the spores are purplish-brown. Hypholoma fasciculare
basidiocarps are inedible and bitter to
taste. They cause gastro-intestinal irritation and
there are occasional reports of death following
ingestion (Lincoff & Mitchel, 1977). Hypholoma
fasciculare is highly competitive against other
wood-rotting fungi. It is capable of extending
from a woody food base through the soil by
means of mycelial cords in search of further
woody substrata. It can also utilize leaf litter. As
a wood-decaying fungus its strategy is secondary
resource capture, i.e. the displacement of
other fungi which have earlier colonized wood,
killing their mycelia. It therefore tends to fruit
late in succession (Rayner & Boddy, 1988; Boddy,
1993).
Pholiota (c. 150 spp.)
Most species of Pholiota grow on wood. Pholiota
squarrosa is associated with soft, pale brown-rot
(butt rot) of living trees of ash (Fraxinus), beech
(Fagus) and poplar (Populus). Dense clusters of
scaly brown basidiocarps are formed at the base
of the trunk (Plate 9e). There is a prominent ring
on the stem and the spores are smooth and
rusty brown. It is best to avoid eating the
basidiocarps of Pholiota spp. because serious
ill-effects may follow, especially if they are
consumed with alcohol. However, the nameko