1) Alga 2) Bladderwrack 3) Fucus 1) Brown algae 
• (n.) Any coarse seaweed growing on sea-washed rocks, especially Fucus.
common name for various species of brown algae growing attached to intertidal rocks. See Fucus; Sargassum.
Rock'weed` noun (Botany) Any coarse seaweed growing on sea-washed rocks, especially Fucus. 
[n] - coarse brown seaweed growing on rocks exposed at low tide
noun coarse brown seaweed growing on rocks exposed at low tide