202 PHYLUM V. PHAEOPHYCEAE 
310. In common Rockweeds (Fucus) of the seashore 
the sexual organs are found in the thickened ends of the 
lateral branches. They occur on the walls of cavities 
(conceptacles), which are spherical, with a small opening 
at the top. The conceptacles are at first portions of the 
general surface, and afterward become depressed and 
walled in by the overgrowth of the surrounding tissues; 
they are thus in reality portions of the general surface. 
311. The walls of the conceptacles are clothed with 
pointed hairs, which in some species project through the 
opening, and among these are found the sexual organs. 
The antherids are produced as lateral branches of hairs; 
each antherid is a thin-walled structure containing a 
large number of biciliated sperms, which escape by the 
rupture of the surrounding wall. Before rupturing, 
however, the antherids detach themselves and float in the 
water with their contained sperms. 
312. The oogone is a globular or ovoid short-stalked 
body containing eight eggs. These escape from the 
oogone and float out through the opening of the concep- 
tacle, into the open water. The sperms, which are lib- 
erated at about the same time, gather around the 
inactive eggs in great numbers, and by the vigor of 
their movements sometimes actually give them a rotary 
motion. Fertilization results from the union of one of 
these sperms with the egg, the zygote thus produced 
secreting a wall of cellulose about itself. 
313. In germination the zygote lengthens and under- 
goes division into numerous cells; at the same time it 
elongates below into root-like processes, which serve to 
hold fast the new plant. 
314. In the nearly related Gulfweeds (Sargassum) the 
plant body is composed of a distinct stem, rooted below, 
and bearing leaves above. The stem bears also many 
