Description:
The life-history involves an alternation between morphologically different gametophyte and tetrasporophyte.
Gametophyte plants occurring from March-June, brownish-red, fronds feathery, with a slightly flattened axis to1 mm wide and 350 mm long, attched to Cystoseira and other algae by crozier-shaped, hook-like modified branches.
Tetrasporophyte ("Trailliella intricata phase") plants occurring all year round, but most obvious in October-March, brownish-red, much branched, filamentous, in dense cotton-wool-like tufts to 25 mm in diameter.

(In: Seaweed Site -©Michael D. Guiry - http://seaweed.ucg.ie/descriptions/Bonham.html)

Habitat: Probably introduced from Japan or its environs, at the end of the last century; gametophyte first found in Europe (Isle of Wight) in 1893, on rocks and other algae, lowest intertidal and subtidal, southern and western coasts, rare. Tetrasporophyte first recorded in British Isles (Dorset) in 1890, epiphytic on Corallina officinalis, lower tidal pools and subtidal, now widely distributed on southern and western coasts to Shetland Isles, frequent and can be abundant in certain locations, notably where there are large, lagoon-like lower intertidal pools.

(fotografia obtida nos Açores)