Introduction to Fungi, Third Edition

EUROTIALES
309
Fig11.16 Eurotium repens. (a) Conidiophore.
(b)Ascogonium.(c)Ascogoniumsurroundedbysterile
hyphae. (d) Cleistothecium showing mature and
immature asci.
surrounding pseudoparenchyma derived from
the investing hyphae. Globose asci develop from
croziers at the tips of the ascogenous hyphae
and, when ripe, the ascocarp consists of clusters
of asci surrounded by a single-layered, yellowcoloured
peridium. The peridium breaks open
irregularly. The asci do not discharge violently,
but the ascospores escape as the ascus wall
breaks down. The ascospores are broadly lenticular,
and are without obvious surface ornamentation
in E. repens, although they may bear an
equatorial furrow in other species.
Eurotium repens, like nearly all Eurotium spp.,
is homothallic, and cultures can be transferred
by means of conidia, ascospores or hyphal tips.
If successive conidial transfers are made, the
ability to form ascospores declines with each
transfer. Ascospore production can be restored to
the initial level by making one subculture from
an ascospore (Mather & Jinks, 1958). This suggests
that the formation of cleistothecia and conidiophores
is partially controlled by cytoplasmic
determinants, and it also indicates a way
in which purely anamorphic forms may have
evolved from Eurotium. Little recent work seems
to have been carried out on sexual reproduction
in Eurotium.
Emericella
Emericella differs from Eurotium in a number of
features. Whilst in Eurotium the ascocarp is eventually
surrounded by a single-layered peridial
envelope, that of Emericella is enclosed by chains
of very thick-walled cells termed Hülle cells