Petalonia fascia (O.F.Müll.) Kuntze

Scientific Description

Habit and structure. Thallus medium to dark brown, flat, simple or split above, broadly lanceolate to ligulate with a cuneate base, 5–30 cm high and (0.5–)1–6 cm broad, with one to several fronds from a small discoid holdfast 0.5–1(–2) mm across; epiphytic or epilithic. Structure polystichous, 100–300 µmthick, with a medulla 2–4(–8) cells thick, of large and small, clear, irregularly placed cells and a cortex 1–2 cells thick, outer cells more or less in longitudinal rows, isodiametric, 6–8(–10) µmacross in surface view; phaeophycean hairs rare to frequent, single or in small groups, scattered, becoming sunken in a pit, 4–6 µmin diameter; cortical cells with a single phaeoplast and pyrenoid, with scattered or grouped cells in some specimens with uniform, yellowish, darkly-staining contents.

Reproduction. Sori extending over most of the surface, often in longitudinal patches, without paraphyses (but including the yellowish cortical cells when present); plurilocular organs 20–30 µmand 4–6 locules high, 6–8 µmin diameter, consisting of 4(–8) vertical rows from each cortical cell.

Distribution.In Australia, from the Murchison River mouth, W. Aust., to Manly, N.S.W., and around Tas.

Habitat. The erect stage is found throughout the winter (May to October), epilithic or on Amphibolis and Posidonia.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 292–293 (1987)]