Fucus

Fucus, an important genus of olive-brown seaweeds, giving its name to the order Fucaceee, and including the common bladder-wracks (F. vesiculosus and F. nodosus), which cover so large an area of the tidal rocks of our coasts. They have a flat thallus, brandling in one plane, often with large air-bladders hollowed out of their tissue as floats. The only known method of reproduction is sexual, the antheridia and oogonia being, either together (monoecious) or separately (dioecious), in globular cavities, known as conceptaclcs, sunk in the warty extremities of the branches. The antheridia are lateral or branched hairs (hyphen), and the protoplasm of each ovoid antheridium breaks up into numerous pointed and laterally biciliate antherozoids. The oogonia terminate short hypbee, and their contents break up into eight relatively large oospheres. These escape from the conceptacle through its ostiolv or mouth into the water; are impregnated by numerous antherozoids, the cilia of which impart to them for a time a rolling movement; and, acquiring-a cell-wall and settling down, germinate by cell-division without any resting period. They are largely used in the manufacture of kelp (q.v.), as a source of iodine and as a manure. F. vcsiculosits is the badge of the clan M'Neill.