Dasya haffiae Harv.

Scientific Description

Habit and structure. Thallus pale crimson-red to dark red-brown, 15–30 cm high, usually with a single axis. Main axis corticated, 1–2 mm in diameter, regularly to irregularly distichously branched often from very close to the apex; lateral axes usually regularly distichously branched, occasionally radially, ultimately bearing spirally arranged, subdichotomous, monosiphonous pseudolaterals. Holdfast discoid, epilithic. Structure. Pericentral cells 5, developed in circular sequence, becoming obscured in transverse sections of older axes by rhizoidal cells which may become much enlarged. Pseudolaterals one on each segment, 250–1100 µm long, patent and curved, tapering to an acute apex or rarely forming an attenuate filament, below subdichotomous every 2–3 cells with 3–5 subdichotomies giving 6–20 ultimate branches. Basal cell and lower cells 20–45 µm in diameter, L/D 1–2(–2.5). Adventitious monosiphonous filaments scattered, arising from cortical cells, unbranched and acute, or subdichotomous resembling smaller pseudolaterals. Intercalary cell divisions absent. Lateral axes arise from the basal cell of the first branch of the pseudolateral, with adventitious lateral axes arising from surface cortical cells, scattered on older parts of the main axes. Rhodoplasts discoid, chained and reticulate even in smaller cells.

Reproduction. Gametophytes dioecious. Procarps spirally arranged on successive segments of lateral polysiphonous and adventitious axes. Carposporophytes with a basal fusion cell and ovoid to subspherical carposporangia, in apical and lateral rows of 2–3. Cystocarps basally embedded in a corticated axis, urceolate, 400–800 µm in diameter, with a distinct neck 0.3–0.5 of the cystocarp diameter in length, either straight or flared with the terminal filaments often extended and free; pericarp 3–4 cells thick, surface often with smaller, simple or subdichotomous, patent, adventitious, monosiphonous filaments. Spermatangial branches sessile or on a 1–2-celled monosiphonous stalk, on the lower branches of the pseudolaterals or adventitious filaments, cylindrical, 170–400 µm long and 45–60 µm in diameter, with or without a short apical filament (1–)3(–5) cells long, the apical cell being conical. Stichidia on a 1–2-celled monosiphonous stalk, on the lower branches of the pseudolaterals or adventitious filaments, cylindrical or occasionally ovoid, (80–)110–200(–410) µm long and 70–80(–90) µm in diameter, with (2–)3–12(–20) fertile segments each with (4–)5 pericentral cells all of which usually become fertile, the basal segment of 4 pericentral cells with 1–2(–3) becoming fertile. Each tetrasporangium with 2–3 cover cells, round to broader than high in surface view, which cover less than one quarter of the sporangium and are often moulded around the sporangium.

Distribution. Geraldton, W. Aust., to Walkerville, Vic., and around Tas.

Habitat. D. haffiae occurs sublittorally, down to 23 m, often on limestone.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 439–441 (1998)]