Introduction to Fungi, Third Edition

406 HYMENOASCOMYCETES: ERYSIPHALES
Fig13.12 Sphaerotheca (now Podosphaera)
pannosa. (a) Chasmothecium crushed to show
a single ascus. (b) Chasmothecium with
discharged ascospores.
gives rise to very large and distinctly shaped
conidia.
13.7.1 Phyllactinia
Phyllactinia guttata (¼ P. corylea) grows on the
leaves of hazel (Corylus avellana) and other woody
plants, forming chasmothecia on the lower leaf
surface in late summer and autumn. In this
species the superficial mycelium produces short
lateral appressoria which emit penetration
hyphae through the stomata into the mesophyll
(Fig. 13.13b). Directly beneath the stoma, the
penetration peg swells to produce a substomatal
vesicle from which septate hyphae grow into the
leaf mesophyll, penetrating mesophyll cells and
forming haustoria within them. The conidia are
club-shaped and are formed singly (Fig. 13.13a).
However, in a damp chamber pseudo-chains of
up to four conidia may hang together. Conidia
of this type are classified in the anamorphic
genus Ovulariopsis.
Phyllactinia guttata presents a most intriguing
spore dispersal mechanism which is easily demonstrated
in mycology classes because the same
hazel trees are reliably infected each year and,
once a source has been located, leaves can be