Dasya ceramioides Harv.

Scientific Description

Habit and structure. Thallus dark brown to red, or pale rose-red, 10–30(–40) cm high with 1–2(–5) pyramidal main branches with corticated axes 1–1.5(–2) mm in diameter. Main axes sympodial, becoming irregularly radially branched (sometimes pseudolaterals subdistichous) with 2–10(–15) well developed laterals arising at intervals of 2 mm to 1(–2) cm, bearing basally branched, attenuate, large celled, pseudolaterals. Laterals corticated from close to apices, arising from the basal cell of the first branch of the pseudolateral. Adventitious laterals not formed. Holdfast discoid, 2–8(–14) mm across; on solid substrates. Structure. Pericentral cells 5, remaining prominent in sections at all ages, with slender rhizoidal filaments surrounding the individual pericentral cells and the central cell, later thickly covering the whole surface. Pseudolaterals one per segment, 1.5–3(–4.6) mm long, simple or with 1–2 basal subdichotomies giving (1–)2–3(–4) ultimate branches 8–10 cells long, cells relatively large, 80–230 µm in diameter and L/D 0.3–1 near the base, increasing to (120–)160–300 µm in diameter and L/D 2–3(–4) in mid filament, then tapering to 2–3 very small terminal cells in an acute apex, occasionally terminating in an attenuate, pale filament. Adventitious monosiphonous filaments absent. Rhodoplasts discoid to elongate, becoming chained.

Reproduction. Gametophytes dioecious. Procarps borne spirally on successive segments of polysiphonous axes. Carposporophytes with a slight basal fusion cell and ovoid to subspherical carposporangia, in rows of 2–4. Cystocarps sessile, terminal or nearly so on lateral branches, single or rarely paired, urceolate, 550–800 µm in diameter with a prominent neck 0.3–0.7 as long as the cystocarp diameter; pericarp 3–4 cells thick, outer cells relatively large and irregularly shaped. Spermatangial branches in clusters of 2–6 near the base of the pseudolaterals, on monosiphonous stalks, cylindrical to slightly attenuate, 350–750(–900) µm long and 40–70(–80) µm in diameter, with 8–10(–15) fertile segments and often a short, 1–2(–3)-celled sterile apex. Stichidia in clusters of 2–5 near the base of pseudolaterals, on 3–6-celled monosiphonous stalks, cylindrical with slightly curved attenuate apices, 300–700(–1000) µm long and 50–200 µm in diameter, with 10–25 fertile segments each with 6 pericentral cells all of which produce tetrasporangia. Tetrasporangia 25–45 µm in diameter, each with 3(–4) cover cells which lengthen to 1–1.5 diameters long and cover about 75% of the tetrasporangium.

Distribution. Port Denison, W. Aust., to Sealers Cove, Vic., and the N and E coasts of Tas.

Habitat. D. ceramioides is a deep-water or shade species, fertile in late spring and summer.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 443–446 (1998)]