Fig. 229.
Contact of
antheridium
and carpogonium
(carpogonium
the larger cell);
beginning of
fertilization.
Fig. 230.
Disappearance of
contact walls of
antheridium and
carpogonium,
and fusion of
the two nuclei.
Fig. 231.
Fertilized egg surrounded
by the enveloping threads
which grow up around it.
Figs. 229-231.—Fertilization in sphærotheca; one of the powdery mildews.
(After Harper.)
415. Number of spores in an ascus.—The ascus is the most important character showing the general relationship of the members of the sac fungi. While many of the powdery mildews have a variable number of spores in an ascus, a large majority of the ascomycetes have just 8 spores in an ascus, while some have 4, others 16, and some an indefinite number. The asci in a perithecium are more variable. In some ascomycetes there is no perithecium.
Fig. 231a.
Edible Morel. Morchella esculenta.
The asci, forming hymenium, cover the pitted surface.