Dictyopteris australis (Sond.) Askenasy

Scientific Description

Habit and structure. Thallus medium brown, usually 10–30 cm long, with one to several complanate fronds arising from a matted rhizoidal holdfast 0.2–1.5 cm across and 0.2–1.0(–1.5) cm long; epilithic. Growth from several apical cells in a rounded apex. Fronds subdichotomously branched at intervals of 3–10 cm, with or without proliferous branchlets from adjacent to the midrib, of fairly uniform width (usually 0.8–1.5 cm) throughout, with a central midrib and usually with faint (microscopic) lateral veins, less than 1.5 mm apart, running upwards from midrib to margin; branches often denuded below. Structure of wing of cells of similar size, one cell thick (25–40 µm) within 4–10 cells of the margin, becoming two cells thick (60–90 µm) for most of the wing, and 3–4 cells thick near the midrib which is usually 8–10(–14) cells thick and has a central core of slenderer cells; cortical cells 16–30 µm across in surface view and L/B(1–)2–5. Hair tufts dense, arranged in reflexed slight curves from midrib to margin; hairs originating from small lateral derivatives of cortical cells, 14–22 µm in diameter.

Reproduction. Sporangial sori associated with the hair tufts and forming reflexed lines from midrib to margin, rarely extending over the blade; sporangia external to the cortex, with a laterally elongate stalk cell within the blade, subspherical, 100–160 µm in diameter. Oogonial sori unknown. Antheridial sori scattered, irregularly angular in shape, sunken within the thallus, 400–1500 µm long, 200–1000 µm across; antheridia 25–50 µm long, 20–50 µm in diameter.

Distribution.From One Arm Point, W. Aust., around southern Australia to Port Noarlunga, S. Aust. Qld., Lord Howe I.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 222–224 (1987)]