Mazzaella japonica

Thallus blade-like, cartilaginous, 10–20(–30) cm high, purplish-red, to yellowishclaret color (with more light upper parts), with narrowly-cuneate stalk, bearing cuneate simple blades or branched into 2–3(–6) lobes with entire, wavy or sometimes proliferating margins. In transverse section, cortex composed of small outer cells, 4–5×6–10 mm increasing to roundish cells of the inner cortex; medulla of loosely arranged filaments composed of long cells (to 170 mm) and 4(–11) mm wide with lateral outgrowths (branches) when connect with neighboring cell. Cystocarps spherical or sometimes flattened, 0.6–1(–2) mm diam., prominent on both sides of thalli. Tetrasporangial sori to 0.5 mm across. Attachment by holdfast. Growing in intertidal pools and subtidal zone, on rocky bottom.

Asia: China, Korea, Japan (Hokkaido, Honshu Isls), Russia.