Undaria pinnatifida

Thallus blade-like, flat, oval, broadlylanceolate to triangular in outline, pinnately parted, with midrib, soft, smooth, lubricous, 0.5-1(-1.5) m long, 0.5-1(-1.5) cm broad, olive to dark-brown. Stipe flattened gradually transform into flat midrib of the blade. In transverse section the blade consist of superficial meristematic cell layer, cortex and medulla. Meristematic cells small, densely arranged; cortical cells large, loosely arranged and medulla composed of entangled filaments. Sporangia develop in slimy undulate-folded sporophylls on both sides of the stipe. Gametophyte microscopic composed of branched filaments. Attachment by dichotomously branched rhizoids. Growing on rocks, stones, in low intertidal to 15 m deep, in open and sheltered shores.

Europe. Temperate waters of Atlantic and Pacific Oceans. Asia (China, Japan, Korea, Russia), Australia and New Zealand.