398 REPRODUCTIVE ORGANS OF ALG#.—(CDOGONIUM. 
formed secretes around itself a cell-wall and very soon begins to 
germinate. Growth and division proceed, and so a new Fucus 
thallus is built up. 
(Hdogoivium.—The thallus of Gdugoniwm consists of a long, 
unbranched row of cells; and each cell is nucleated, and con- 
tains chlorophyll granules imbedded in the parietal protoplasmic 
layer. Reproduction is 
effected either asexually 
by means of zoospores; or 
in a sexual manner by 
antheridia and oogonia. 
The former are produced 
by means of the bursting 
of a cell and the conse- 
quent escape of the cell 
contents in the form of 
an ovate mass with a tuft 
of fine cilia at the more 
pointed extremity. 
In the latter case the 
antherozoids are formed in 
special cells, and either 
on the same filament as 
the oogonia (fig. 869, 4, 
n, og); which is then 
termed a sexual filament ; 
or on another filament 
(fig. 869, c, 2, 2%), then 
called a male filament. 
Theantherozoids resemble 
the zoospores or zoogoni- 
dia, but are smaller. The 
vogonia (fig. 869, A, og, og) 
are oval bodies containing 
a great deal of chlorophyll, 
and are formed by the 
enlargement of any of 
the individual cells of the 
filament. The contained 
protoplasmic mass, or 00- 
sphere, may be fertilised 
Fic. 869. 
Fig. 869. A. Middle part of asexual filament 
of Bdogonium ciliatum. og, og. Oogonia 
fertilised by the dwarf male plants, m, m, 
developed from zoospores formed in the 
cells, nm (antheridium ), at the upper part of 
the filament. B. Ripe oospore. c. Piece 
of male filament of a species of Ldogonium, 
with production of antherozoids, z,z. D. 
The four swarm-spores resulting from an 
oospore. E. Swarm-spore at rest. After 
Pringsheim. 
in two different ways. 
Hither the oosphere is 
directly fertilised by con- 
tact with the antherozoids 
above described (fig. 869, 
C, 2, 2); or by means of an antherozoid produced from a peculiar 
form of swarm-spore known as an androspore (fig. 869, A, 1). 
The androspore, which is preduced from cells resembling those 
