Introduction to Fungi, Third Edition

590 HOMOBASIDIOMYCETES: GASTEROMYCETES
Fig 20.8 Sphaerobolus stellatus. (a) V.S. of nearly ripe gasterocarp showing the central glebal mass (peridiole) surrounded by a
six-layered peridium. (b) Details of the peridial layers:1, outermost layer composed of interwoven hyphae; 2, layer in which the
hyphae are separated by extensive mucilage; 3, pseudoparenchymatous layer; 4, fibrous layer; 5, palisade layer; 6, layer of lubricating
cells; gl, outer layers of glebal mass. (c) Enlarged portion of layers 4 6 and portion of the glebal mass: c, cystidia; g, gemmae;
b, basidiospores. (d) Clusters of basidia from unripe gasterocarps.There are usually 4 6 basidiospores. (e) Gemmae.
(f) Basidiospores. (c, e) and (f) to same scale.
ensuring that the glebal mass is projected
towards the light (Alasoadura, 1963). Peridiole
discharge follows a diurnal rhythm, with
release occurring during the light phase. In
continuous light rhythmic discharge ceases, but
in continuous darkness a culture previously
exposed to alternating periods of 12 h of light
and darkness continues to discharge peridioles
rhythmically at times corresponding to the
previous light periods, indicating an endogenous
circadian rhythm.
The spherical peridiole (glebal mass) is
surrounded by a dark brown sticky coat derived
from the breakdown of the cells of the innermost
peridial layer. Immediately within the brown
outer coat of the glebal mass are layers of rounded
cells sometimes termed cystidia (Fig. 20.8c).
Apparently these cells are incapable of germination
and their function is not known. The rest of
the glebal mass consists of oval thick-walled
haploid basidiospores and thinner-walled dikaryotic
gemmae. About 4 8 basidiospores develop
on the basidia some 2 days before discharge (Fig.
20.8d), but the basidia disappear as the glebal
mass ripens. Gemmae arise either terminally or in
an intercalary position on hyphae within the
glebal mass. Oil-rich cells are also present. The
sticky peridiole adheres readily to objects on
which it is impacted, and after drying it is very
difficult to dislodge even by a jet of water.
Peridioles are viable for several years. Projectiles
adhering to herbage may be eaten by animals, and
this may explain the presence of fruit bodies on
dung.
On germination the peridioles give rise to
clamped hyphae which usually arise directly from
the gemmae and not from the basidiospores. Most
basidiospores, if they germinate, give rise to
mycelia with simple septa. Pairings of monosporous
mycelia have indicated that the fungus is
usually heterothallic, although details of the
mating system still appear unclear at present.
20.5.3 Phallaceae: stinkhorns
An original solution to the problem posed by the
loss of active basidiospore discharge has been
developed also by members of the Phallaceae
which attract insects, especially cadaverfeeding
flies such as bluebottles, to visit their
gasterocarps. Attraction may be by the emission