Introduction to Fungi, Third Edition

DEVELOPMENT OF BASIDIA
489
Fig18.2 Some different kinds of basidia. (a) Longitudinally divided basidium of Exidiaglandulosa (Tremellales). (b) Tuning-fork type
of basidium of Calocera viscosa (Dacrymycetales). (c) Transversely divided basidium of Auricularia auricula-judae (Auriculariales).
(d) Germinating chlamydospore of Ustilago avenae (Ustilaginales). A transversely septate promycelium has developed and each
segment is forming sporidia. (e) Germinating teliospore of Puccinia graminis (Uredinales). A transversely septate promycelium has
developed and each segment is producing a single basidiospore.
and has particularly large basidia. A detailed
description of the process has been given by
Corner (1948) for O. canarii. Ultrastructural
studies have also been made on a range of
fungi with holobasidia, e.g. the split-gill
(Schizophyllum commune; Wells, 1965), the agarics
Coprinus cinereus (McLaughlin, 1973, 1977, 1982)
and Panellus stypticus (Lingle et al., 1992), the
clavarioid fungus Clavicorona pyxidata (Berbee &
Wells, 1989) and the bolete Boletus rubinellus
(McLaughlin, 1973; Yoon & McLaughlin, 1979,
1984).
18.3.1 Cytological aspects
In Oudemansiella radicata the basidium arises as
the terminal cell of a hypha making up the gill
tissue on the underside of the cap of the fruit body
(basidiocarp). Basidia are packed tightly together
in the hymenium at the surface of the gill. A
basidium is at first filled with dense cytoplasm,
but soon several small vacuoles appear near its
base. Later these coalesce into a single large
vacuole at the base of the basidium and, by
enlargement of this vacuole, cytoplasm is pushed
towards the apex of the basidium. A clear cap is
differentiated at the tip and it is in this region
that the sterigmata develop. Corner (1948) postulated
that there must be four elastic areas in the
upper part of the basidium wall from which
the sterigmata extend. The wall of the upper part
of the basidium consists of two layers, the outer of
which is mucilaginous, the inner firmer. In the
areas where the sterigmata are about to bulge
out, a new layer of wall material is deposited
between these two original layers. The outer
mucilaginous layer of the basidial wall bursts
and the apex of the sterigma grows out. It is
surrounded by two wall layers, the inner of which
is continuous with the inner wall layer of the
basidium (Clémençon, 2004). Ultrastructural
studies of Boletus rubinellus show that, in the
region where the sterigmata appear, the basidial