Introduction to Fungi, Third Edition

468 LOCULOASCOMYCETES
Fig17.9 Pleospora herbarum. (a) Ascus and ascospores showing mucilaginous epispore. (b) Stretched bitunicate ascus showing
rupture of outer wall. (c) Developing asci and pseudoparaphyses.The arrows (p) indicate points of branching of ascending and
descending pseudoparaphyses. (d) Conidia of Stemphylium type.
(Weber & Webster, 2000b). The P. herbarum
complex includes a number of similar species
forming conidia which are critically different
from each other in morphology and dimensions
(Simmons, 1969). A distinctive form,
S. vesicarium, is associated with leaf blight of
onions and garlic.
Stemphylium conidia develop singly from the
tips of conidiophores swollen at their apices,
as blown-out ends. A narrow neck of cytoplasm
connects the developing spore to its conidiophore
through a pore, and Hughes (1953) has
termed conidia of this type porospores
(Fig. 17.9d), but the term poroconidium is also