Introduction to Fungi, Third Edition

DACRYMYCETALES
599
Fig 21.4 Dacrymyces stillatus. (a) Basidiospores showing germination by germ tubes or formation of conidia (bottom). (b) Basidia.
Note that the attached basidiospores are unicellular.They become three-septate on germination. (c) Arthrospores from a conidial
pustule.
are surrounded by parenthesomes without
perforations (Wells, 1994). The probasidium
arises from a dikaryotic hypha and is initially
club-shaped. At this stage karyogamy occurs and
is immediately followed by meiosis. Meanwhile
the two epibasidia develop. Each of the two
basidiospores seems to receive one nucleus, and
the remaining two nuclei degenerate in the
epibasidia (see Wells & Bandoni, 2001). Before
the basidiospore germinates, it lays down one or
more septa. Each spore segment can produce a
haploid monokaryotic hypha or may give rise to
conidia which in turn germinate by means of
monokaryotic germ tubes (Ingold, 1983b). It is
unclear in many species how and where dikaryotization
occurs, but it is probably by fusion
of monokaryotic hyphae. Mating systems, where
known, are bifactorial (tetrapolar), i.e. with two
mating type loci A and B.
Members of the Dacrymycetales are saprotrophic
on wood and cause brown-rots, although
some lignin degradation has also been observed
(Seifert, 1983; Worrall et al., 1997). The fruit
bodies are common on decaying wood, including
wood built into outdoor structures such as park
benches or fences. There are about 70 species,
and the order is monophyletic (Oberwinkler,
1993). Reid (1974) has given keys and descriptions
of the common British and European species.
The seminal features of the order have been
summarized by Wells (1994) and Wells and
Bandoni (2001).