in botany, a genus of submarine plants, belonging to the cryptogamia class.

The fucus consists of a tough matter, formed into a kind of leaves, which are flat and variously divaricated; and which have some appearance of fructification, in punctated tubercles, covering oblong vehicles, supposed by Linnaeus to be male flowers; and smooth roundish vehicles, hollow and interwoven with filaments, which appear to him to be female flowers. There are thirty-four species of fucus, or sea wrack, many of them to be found on our coasts.