Introduction to Fungi, Third Edition

234 ASCOMYCOTA (ASCOMYCETES)
Fig 8.8 Conidiogenesis inThielaviopsis basicola.
(a) Phialides and phialoconidia.To the left is a
branched conidiophore with a short phialide
which has not yet formed conidia and a longer
phialide in which the tip has broken
transversely and the first phialoconidium is
being extruded.This spore is capped by the
remnants of the phialide tip. Developing
phialoconidia can be seen in the necks of the
phialides. (b) Three end spores from a spore
chain.The capped terminal spore is more
bulbous than the cylindrical spores which
succeedit. (c) A branched conidiophore bearing
two phialides with chains of hyaline thin-walled
phialoconidia and a dark, thick-walled
transversely septate chlamydospore.These
two distinct conidial states are synanamorphs.
Scale bar: (a) ¼ 10 mm, (b) ¼ 20 mm.
Hypocrea; see Fig. 12.16). Phialoconidia are, in
general, unicellular but multicellular conidia
are found in certain genera such as in the transversely
septate conidium of Sporoschisma (conidial
Melanochaeta; for references see Sivichai et al.,
2000).
Annellidic conidiogenesis (Fig. 8.7) in many
ways resembles phialidic, and indeed the term
annellidic phialide is sometimes used for this
type of conidiogenous cell. These are also termed
annellides (Lat. annulus ¼ little ring) or annellophores,
and the spores which develop from them
are annelloconidia. As in phialidic development,
the first-formed annelloconidium is holoblastic.
The difference between the two modes of
development is that new wall material which is
secreted within the annellide protrudes beyond
its neck and the septum which cuts off the newly
formed conidium also forms beyond the neck.
As each new conidium develops in basipetal
fashion, a small ring of wall material (annellation)
is left at the neck of the annellide, which
thus grows in length as successive conidia
develop. This accumulation of short collars of
wall material is the annellated zone (see Fig. 8.7).
With normal light microscopy annellation may
be difficult to see, but detection is improved by
interference contrast or phase contrast optics.
Examples of fungi reproducing by annelloconidia
are Scopulariopsis brevicaulis (see Fig. 12.38;
Cole & Kendrick, 1969a) and Cephalotrichum
(Doratomyces) stemonitis (Fig. 12.39). Both genera
contain species which are conidial forms of
Microascus.