Fucus
Fucus , noun
[Latin rock lichen, orchil, used as a red dye, red or purple color, disguise, deceit.]
1.
A paint; a dye; also, false show. [Obsolete]
2.
(Botany) A genus of tough, leathery seaweeds, usually of a dull brownish green color; rockweed.
Formerly most marine alga were called fuci.