Sargassum pinnatifidum

Thallus coarse, bushy, 0.5 m high. Main axis compressed. Branching distichously pinnately. Phylloids at the lower portion narrow, linear, 1-2 mm broad, to 5 cm long, subdichotomously divided or simple, with immersed midrib vanishing below the apices and with the margins sharply toothed or sometimes entire. Cryptostomata absent. Phylloids on the upper branches decompound, pinnate, thin, membranaceous, to 8 cm long with dentate margins and cryptostomata irregularly scattered on both sides of the phylloids. Vesicles solitary, oblong, ellipsoidal or sometimes subspherical, 3–5 mm diam., mucronated or with simple or bifurcated leaflets at the top, on stalk shorter than their diameters, borne at the base of lateral branchlets. Receptacles long-cylindrical, non-spinose, racemose. Attachment by discshaped holdfast to rocks.

China, Hong Kong, Korea, Japan.