A weed growing upon the sea shore, and in cold situations; called also ulva,facus marinus, bryon thalassium, grass-wrack, wrake, sea-weed or Grass,. and sea-moss.

There are three kinds distinguished by La Muck: the first, filamentous, gelatinous, and membranous; the second, with more decided appearances of fructification; the third, with those parts more obvious, and opening to scatter the farina or deposit seeds. Some of the species are employed in the manufacture of kelp on the coast of Scotland; but in medicine their powers are, perhaps, principally owing to the sea salt they contain, and little choice is necessary. The bladder oar-weed, fucus vesiculosus, has been preferred, but with little reason. On the coast of the Mediterranean sea a species of alga is gathered and dried to feed oxen.

The seeds of the alga are more perfect than those of the fuci, for its vessels gape when perfect, and the seeds fall out. Stackhouse Nereis Britannica, Major Velley on Marine Plants; Turner on Fuci, Linnaean Transactions, vol. iii.

Alga marina latifolia vulgatissima, the common sea-wrack, see Kali.