Introduction to Fungi, Third Edition

OTHER REPRESENTATIVES OF THE HELOTIALES
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Fig15.10 Rhytisma acerinum. (a) T.S. living leaf of Acer pseudoplatanus in June showing spermogonium. (b) Details of cells forming
spermatia. (c) T.S. overwintered leaf of Acer showing the opening of lips of the stromatal surface to reveal the apothecial hymenium.
(d) Asci, paraphyses and ascospores. Note the mucilaginous appendage at the upper end of the ascospore.
unusually shaped or brightly coloured fruit
bodies. Good images and keys are given in
Dennis (1981), Breitenbach and Kränzlin (1984)
and Hansen and Knudsen (2000). Very little
is known about Helotiales with small or inconspicuous
apothecia, such as the Hyaloscyphaceae
(Plate 7e).
15.5.1 Geoglossaceae
Trichoglossum is a representative of the Geoglossaceae
(earth-tongues) which form club-shaped
stalked apothecia. Members of this family grow
saprotrophically on the ground, but sometimes
also on dead leaves or amongst Sphagnum
(e.g. Mitrula). An account of the family has been
given by Nannfeldt (1942). Trichoglossum hirsutum
has black, somewhat flattened fruit bodies up
to 8 cm high, and grows in pastures and lawns.
The ascospores are long, dark and septate, and
the asci are interspersed by black, thick-walled,
pointed hymenial setae whose function is not
known (Fig. 15.11b). The presence of hymenial
setae separates Trichoglossum from Geoglossum
which grows in similar habitats. The elongated
ascospores of Geoglossum and Trichoglossum are
discharged singly through a minute pore at the
tip of the ascus. When the ascus is ripe, the
pore bursts and one ascospore is squeezed into
it, blocking it. The pressure of the ascus sap
behind the spore causes the spore to protrude,
at first slowly. When about half the spore is
projecting, the spore gathers velocity and is