Halimeda tuna

Thallus compact forming clusters, 5-6(-20) cm high, light, light dull-green, bright green. Branching in one plane di- trichotomous. Segments lightly calcified, flabellate, rounded triangular, disc-like, 0.8-1.7(-2.0) cm wide, 1.0-1.5 cm long, 1.3 mm thick near base, 500 mm in the middle portion and 1.1 mm thick at margins of segments. Upper margins entire, slightly undulate. Ribs absent. The uppermost utricles in surface view polygonal, (27)-50-100(-150)×90-120 mm. Cortex of 2-4 layers of utricles. Surface utricles 40-150 mm long. Subsurface utricles 90-120 mm diam, 120-250 mm long, each bearing 2-4 surface utricles. Basal segment stipe-like, subcylindrical or subcuneate. Holdfast inconspicuous, small (5-10 mm long). Growing on hard substrate in low intertidal, upper subtidal.

Note: The alga is used in folk medicine (antibacterial activity).

Indian, Pacific Oceans.