REPRODUCTIVE ORGANS OF ALG#.—FUCUS. 397 
oogonia conceptacles are produced in the same plant; such 
species therefore are dicecious. 
Taking Fucus vesiculosus as an example of the dicecious 
species, on making a section through a female conceptacle, its 
cavity is found to be of a more or less spherical form, and 
marked off from the loose tissue of the interior of the thallus 
by a thin layer of denser tissue resembling, and in fact being a 
continuation of, that of the surface, which may be called the 
epidermal layer (fiy. 865). Springing from all parts of the wall 
of the conceptacle are slender jointed filaments, the paraphyses. 
Amongst these paraphyses are the oogonia, which are produced 
from certain cells of the lining, or epidermal layer of cells. 
The antheridia in the moncecious species, as Fucus platyear- 
pus, are developed in the same conceptacle as the oogonia ; and 
Fic. 866. Fia. 867. Fic. 868. 
Fig. 866. Antheridia, a, a,0n the branched hairs of the mate conceptacle. 
After Thuret. Fig. 867. Oogonium with the oospheres fully separated, 
and disengaging themselves from their coverings. After Thuret. Fig. 
868. An oosphere without a cellulose coat being fertilised by antherozoids 
so as to form an oospore. 
in dicecious species in separate conceptacles, then termed male 
conceptacles. These antheridia (fig. 866) are somewhat elliptical 
bodies, a, a, formed on branched hair-like cells. When mature 
the antheridium becomes a bright red colour, and contains a 
number of smal! antherozoids (jig. 868), each of which is fur- 
nished with a pair of cilia. 
The oogonia are globular bodies borne upon a short one- 
celled stalk, in which are produced eight oospheres by means 
of the division of the contained protoplasm (jig. 867). These, 
which are at first angular, become rounded off, and are ulti- 
mately set free by the bursting of the oogonium membrane. 
The antherozoids, which escape almost simultaneously with the 
oospheres, gather round the latter and appear to become finally 
blended with their substance (jig. 868). The oospore thus 
