te
themselves by septa from the tube which carries them. Their membrane
encloses granules of opaque protoplasm, mingled with numerous bulky
granules of colourless fatty matter.

[Illustration: FIG. 98.--Conjugation in _Peronospora; a. antheridium_.
(De Bary.)]

The branches of the mycelium which do not bear oogonia apply their
obtuse extremities against the growing oogonia; this extremity swells,
and, by a transverse partition, separates itself from the supporting
tube. It is the antheridium, or male organ, which is formed by this
process; it takes the form of an obliquely clavate or obovate cellule,
which is always considerably smaller than the oogonium, and adheres to
its walls by a plane or convex area. The slightly thickened membrane
of the antheridia encloses protoplasm which is finely granular. It is
seldom that more than one antheridium applies itself to an oogonium.

The two organs having together achieved their development, the large
granules contained in the oogonium accumulate at its centre to group
themselves under the form of an irregular globule deprived of a proper
membrane, and surrounded by a bed of almost homogeneous protoplasm.
This globule is the _gonosphere_, or reproductive sphere, which,
through the means of fecundation, should become the reproductive
body, vegetable egg, or oospore. The gonosphere having been formed,
the antheridium shoots out from the centre of its face, close against
the oogonium, a straight tube, which perforates the walls of the
female cell, and traversing the protoplasm of its periphery, directs
itself to the gonosphere. It ceases to elongate itself as soon as it
touches it, and the gonosphere becomes clothed with a membrane of
cellulose, and takes a regular spheroidal form.

[Illustration: FIG. 99.--Antheridia and oogonium of _Peronospora_. (De
Bary.)]

Considering the great resemblance of these organs with the sexual
organs of the Saprolegniae, which are closely allied to the Algae, and
of which the sexuality has been proved, De Bary adds, we have no doubt
whatever that the phenomena just described represent an act of
fecundation, and that the tube pushed out by the antheridium should be
regarded as a fecundating tube. It is remarkable that amongst these
fungi the tube projected by the antheridium effects fecundation only
by contact. Its extremity never opens, and we never find antherozoids;
on the contrary, the antheridium presents, up to the maturity of the
oospor