a ae Tr OAT CRN a ee 
it eh 3 MR Wree 
- 270 es ty uctural and Ph psiological Botany. 
under special circumstances (Fig. 402). Reenibling this Tipe 
the mode of reproduction by gemme. Special filaments of = 
the Fungus break up by repeated transverse division intoa 
row of cells capable of germination, which then propagate 
the parent organism by multi- 2 7 
plication in the ordinary manner. : | 
In only comparatively few 
cases 1s a sexual reproduction by 
oospores (embryos) known among 
Fungi, resulting from the reci- 
Fic. 402.—Beer-yeast, Saccharomyces Fic. 403.—Process of impregnation 
(Zorula) Cerevisie. (X 450.) of Saprolegnia moncica: a an- 
theridia; ¢ fertilising tubes 
which penetrate into the oogonium 
ay g + mycelial filaments, 
procal influence on one another of two cells of different 
kinds. In the Saprolegniex (Fig. 403) and Peronosporez 
the female cells or cogonza are spherical, full of protoplasm, | — 
and usually terminal. Their protoplasm collects into one 
or more globular masses, the vospheres, which have at first 
a smooth surface, but no cell-wall. During the formation oy 
of the oogonium slender branches from its pedicel or from 
neighbouring filaments grow out towards it. The upper end 
of one or more of these branches becomes firmly adherent — 
to the oogonium, no longer grows, swells up somewhat, and | 
becomes separated by a septum into an independent cell, 
the fertilising axtheridium. As soon as both the oogonium | 
and antheridium have attained their full size, and the oo- — 
sphere is at least in process of formation, the antheridium i 
puts out one or more beak-like protuberances, the fer 
lising tubes, which pierce the wall of the oogonium. Inthe 
