Dasya scopulifera Harv.

Scientific Description

Habit and structure. Thallus dark red-brown, 20–40 cm high with a stout main axis and long laterals bearing short laterals 2–10 mm apart with tufted pseudolaterals. Main axis usually single, (1.5–)2–4 mm in diameter, very heavily corticated, linear, occasionally slightly swollen between the short laterals, tapering slightly near the apex, smooth and denuded of pseudolaterals; long laterals similar to main axis. Short laterals simple or rarely branched, becoming tufted in older plants, usually 5–15(–30) mm long, irregularly radially arranged, corticated but only 0.3–0.5 mm in diameter, terminating in compact tufts of incurved, large-celled, pseudolaterals. Holdfast conical, 4–10 mm across; probably usually epilithic. Structure. Pericentral cells 5, heavily corticated but usually remaining clear (by enlargement) in transverse sections, with rhizoidal filaments surrounding the pericentral cells and often obscuring them in the laterals. Pseudolaterals one per segment, lost from older branches, 1–2 mm long, subdichotomously branched 2–3(–4) times at each cell near their base with 1–2(–4) basal segments becoming polysiphonous with up to 5 pericentral cells. Upper monosiphonous parts large celled, 90–230 µm in diameter with cells L/D 1.5–2.5(–3), tapering to acute apices. Adventitious monosiphonous filaments absent. Rhodoplasts discoid.

Reproduction. Procarps spirally arranged on several successive polysiphonous segments. Cystocarps sessile on corticated laterals, globose and urceolate, 800–900 µm in diameter with a prominent corticated neck 0.5–1 as long as the cystocarp diameter. Spermatangial branches unknown. Stichidia in clusters at the base of pseudolaterals, on polysiphonous stalks (1–)2–4(–6) segments long with 5 pericentral cells plus small corticating cells, slightly curved, 250–500 µm long and 100–150 µm in diameter, with 5 pericentral cells all becoming fertile. Tetrasporangia 35–45 µm in diameter, each with three cover cells which cover 0.5–0.8 of the tetrasporangium.

Distribution. Port Denison to Bunbury, W. Aust.

Habitat. D. scopulifera is apparently a rare, deep water species known largely from drift specimens, few of which are fertile.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 446–448 (1998)]