Sargassum macrocarpum

Thallus coriaceous, 2-3 m long. Main axis short (7 mm), cylindrical, 4-5 mm diam., bearing several compressed primary branches spirally arranged. Primary branch to 5.5 mm wide with a longitudinal costal elevation and margins with obtuse protuberances at irregular intervals. Apices of the protuberances are round or acute. Phylloids lanceolate to linear in shape, 11 cm or more long, 2.5 cm wide, with percurrent midrib and serrate margins (serration varying from shallow to deep dentation up to the midrib). Double serration common on phylloides in lower to mid part of primary branches. Cryptostomata absent. Vesicles spherical to elliptical, 9-15 mm long and 6-10 mm broad, with mucronate apex or with coronal leaf similar to that on the branch and sometimes with spines on sides. Receptacles compressed oblanceolate to linear racemosely arranged. Attachment by cone-shaped holdfast (12 mm diam.) to low intertidal and upper subtidal rocks.

Japan, Korea.