Dictiosiphon foeniculaceus
(Hudson) Greville, 1830

Thallus coarsely filiform, abundantly branched, yellowish- brown. In transverse- section the central cavity surrounded with a few layers of large colourless cells and with a layer of cortex cells. Unilocular sprangia large, submergrd. Hairs numerous. On stones, in littoral pools and sublitoral, everywhere. Common. Boreal-Arctic species.