Halimeda discoidea Decne.

Scientific Description

Habit and structure. Thallus dark green, drying dark green to pale green, moderately calcified, erect, to 15 cm tall, from a distinct holdfast, epilithic but often with the base buried in sand, in which case the holdfast can incorporate sand and other loose material. Axes dichotomously branched, often unbranched for several segments, generally in a single plane. Segments subcircular, cuneate or reniform, occasionally elongate, often variable in a single thallus, with smooth or lobed margins, 10–20 (–25) mm long, 10–30 (–40) mm wide and c. 1 mm thick. Peripheral utricles polygonal and 40–70 μm diam. in surface view, occasionally fusing laterally, up to 10 borne on disproportionally large secondary utricles 110–200 μm diam. Medullary siphons 35–90 μm diam., fusing completely at nodes in groups of 2 or 3.

Distribution. Reportedly widespread in tropical seas, in W.A. it can be found as far south as the Houtman Abrolhos Islands, off Geraldton.

Habitat. Usually growing on rock, sometimes the rock being partly buried in sand.

[After Huisman & Verbruggen, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 127 (2015)]