Dasya clavigera (Womersley) Parsons

Scientific Description

Habit and structure. Thallus dark red-brown, occasionally paler, slightly mucilaginous, with 1–2(–4) axes, pyramidal in form, (1–)3–15(–60) cm high, axes simple or rarely branched with robust laterals radially or occasionally bilaterally arranged and 2–10(–25) cm long, densely covered with pseudolaterals but often basally denuded. Main axes heavily corticated, 1–2(–3) mm in diameter, percurrent, branched at intervals of 0.5–2 cm. Laterals 2–10(–20) cm long; axes 400–800 µm in diameter, moderately corticated from close to their apices, arising from the basal cell of the fourth branching of the young pseudolateral. Adventitious laterals common in older parts, arising from surface cortical cells near the base of normal laterals, singly or in clumps. Holdfast 2–10 mm across, with one to several erect axes; epilithic or often epiphytic on larger algae. Structure. Pericentral cells 5, becoming obscured in older axes or laterals by profuse development of rhizoids. Pseudolaterals one per segment, spirally arranged, 1–1.5(–2) mm long, the filaments increasing in diameter and length from the basal cell until a few cells after the last subdichotomy, then tapering to a slenderer filament which is often broken off but may have an acute apical cell; basal subdichotomies 3–7, every 1–2(–3) cells, giving 25–40 ultimate branches; basal and lower cells 40–80 µm in diameter, L/D (0.5–)1–2, mid and upper cells 55–100 µm in diameter and L/D 2–3(–4). Adventitious monosiphonous filaments absent. Rhodoplasts discoid to elongate, becoming chained and reticulate.

Reproduction. Gametophytes dioecious. Procarps alternating on the adaxial side of the second, third and fourth segments of the secondary sympodial axes on pseudolaterals. Carposporophyte with a basal fusion cell, gonimoblast much branched, carposporangia ovoid to subspherical, 15–25 µm in diameter, borne singly or in rows of 2–4. Cystocarps sessile on corticated laterals, urceolate, 800–1200(–1400) µm in diameter, with a prominent corticated neck 0.2–0.5 as long as the cystocarp diameter; pericarp 4–5 cells thick, outer cells ovoid, irregularly placed. Spermatangial branches on the lower branches of the pseudolaterals, sessile or on a 1–2-celled monosiphonous stalk, 120–200 µm long and 40–45(–50) µm in diameter with 7–10 fertile segments, terminated by a short, 1–5-celled, apical filament. Stichidia on lower branches of the pseudolaterals, lanceoid to cylindrical, on a 1–2(–3)-celled monosiphonous stalk and with a short apical filament, 200–400(–450) µm long and 80–150 µm in diameter with usually 8–15 fertile segments each with 6 pericentral cells all of which become fertile. Tetrasporangia 30–40 µm in diameter each with 2–3 rather swollen cover cells covering 0.5–0.8 of the sporangium and dividing rarely.

Distribution. Hopetoun, W. Aust., to Westernport Bay, Vic., and the east coast of Tas.

Habitat. Epilithic or epiphytic (mainly on larger brown algae) in the lower eulittoral or upper sublittoral on rough-water coasts, fertile throughout the year.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 459–462 (1998)]