the appearance in the protoplasm of delicate
lines dividing it into numerous polygonal areas which soon become
more distinct, and are seen to be distinct cells whose outlines
remain more or less angular on account of the mutual pressure. When
ripe, the end of the sporangium opens, and the contained cells are
discharged (Fig. 36, _C_). In case they have no membrane, they swim
away at once, each being provided with two cilia, and resembling
almost exactly the zooespores of the white rust (Fig. 36, _D_, _E_).
When the cells are surrounded by a membrane they remain for some
time at rest, but finally the contents escape as a zooespore, like
those already described. By killing the zooespores with a little
iodine the granular nature of the protoplasm is made more evident,
and the cilia may be seen. They soon come to rest, and germinate in
the same way as those of the white rusts and mildews.

As soon as the sporangium is emptied, a new one is formed, either by
the filament growing up through it (Fig. 36, _F_) and the end being
again cut off, or else by a branch budding out just below the base
of the empty sporangium, and growing up by the side of it.

Besides zooespores there are also resting spores developed. Ooegonia
like those of _Vaucheria_ or the _Peronosporeae_ are formed usually
after the formation of zooespores has ceased; but in many cases,
perhaps all, these develop without being fertilized. Antheridia are
often wanting, and even when they are present, it is very doubtful
whether fertilization takes place.[5]

[5] The antheridia, when present, arise as branches just below the
ooegonium, and become closely applied to it, sometimes sending tubes
through its wall, but there has been no satisfactory demonstration of
an actual transfer of the contents of the antheridium to the egg cell.

The ooegonia (Fig. 36, _G_, _H_) arise at the end of the main
filaments, or of short side branches, very much as do the sporangia,
from which they differ at this stage in being of globular form. The
contents contract to form one or several egg cells, naked at first,
but later becoming thick-walled resting spores (_H_).

CHAPTER IX.

THE TRUE FUNGI (_Mycomycetes_).

The great majority of the plants ordinarily known as _fungi_ are
embraced under this head. While some of the lower forms show
affinities with the _Phycomycetes_, and through them with the algae,
the greater