Padina elegans Womersley

Scientific Description

Habit and structure. Thallus medium brown throughout, lightly calcified on the upper surface, not or only slightly on the lower surface, 4–8 cm long and 4–10 cm in spread, when young flabellate and usually becoming shallowly to occasionally deeply divided, with acute to rounded axils, attached by a rhizoidal holdfast 2–10 mm long and 2–6 mm across; epilithic. Structure of two layers of cells of similar size throughout or with the upper side cells shorter, 70–100 µmthick near the apices and 100–140 µmthick below. Cells in surface view of upper side 20–30 µmbroad, L/B1.5–3(–4), on lower surface 25–35 µmbroad, L/B1–1.5(–2). Hairs in alternating concentric lines on both sides of the thallus, 2–4 mm apart on each side, (12–)14–24 µmin diameter.

Reproduction. Sporangia in concentric, continuous or broken, sori on the upper side of the thallus, above each of the hair lines but with alternate fertile and sterile zones when the hair lines on both sides are viewed together; indusium slight; sporangia ovoid and broad based, 80–100(–120) µmlong and 50–80(–100) µmin diameter. Sexual plants unknown.

Distribution. From the Dampier Archipelago, W. Aust., to Pearson I., S. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 220 (1987)]