Dasya baldockii M.J.Parsons & Womersley

Scientific Description

Habit and structure. Thallus dark red-brown, soft and mucilaginous, 10–35 cm high, with 1–3 corticated axes 1–2.5 mm in diameter, much and irregularly branched, densely covered by basally branched, attenuate, monosiphonous filaments, but occasionally denuded at the base. Holdfast discoid; epilithic. Structure. Pericentral cells 5, not obvious in transverse sections of the older axes, heavily corticated by rhizoidal filaments internally and externally to the pericentral cells. Pseudolaterals one per segment, 1–2 mm long, with 3–5 subdichotomies every 2(1–3) cells on any filament giving 10–20 ultimate branches, distinctly attenuate from the base to beyond the last subdichotomy and then slightly attenuate as an ultimate unbranched filament. Adventitious monosiphonous filaments common, similar to young pseudolaterals, arising from the upper portion of pericentral cells 1 and 3, beginning at about 11 segments from the apex, and also from the later formed cortical cells; occasionally the adventitious filaments are arranged in apparent whorls. Intercalary cell divisions absent or rare. Basal cells of pseudolaterals and adventitious filaments (40–)50–80 µm in diameter, L/D 0.5–1.5; cells after the last subdichotomy 15–30 µm in diameter, L/D 3.5–8; cells of ultimate filament 10–20 µm in diameter, L/D 7–20. Lateral axes arising from the basal cell of the first branch of an adventitious monosiphonous filament. Rhodoplasts discoid to elongate.

Reproduction. Gametophytes dioecious. Procarps borne spirally on a polysiphonous, usually adventitious, axis. Carposporophytes with a basal fusion cell, much branched gonimoblast, and clavate to lachrimiform carposporangia, formed apically and laterally in terminal clusters. Cystocarps sessile on lateral axes, occasionally appearing almost terminal, urceolate, 950–1700 µm in diameter, with a distinct neck 0.2–0.4(–0.5) the diameter of the cystocarp in length; pericarp 3–4 cells thick, outer cells irregularly placed. Spermatangial branches sessile or on a 1–2-celled monosiphonous stalk, on the lower branches of both pseudolaterals and adventitious monosiphonous filaments, elongate-cylindrical, 600–1000 µm long and 80–95 µm in diameter, with 15–25 fertile segments and a 4–9 celled apical filament. Stichidia on the lower branches of both pseudolaterals and adventitious monosiphonous filaments, cylindrical, rarely branched once at the base, sessile or on a 1–2-celled monosiphonous stalk, 200–800 µm long and 110–150 µm in diameter, with 10–25 fertile segments each with (5–)6–7 pericentral cells all of which become fertile. Each tetrasporangium with (2–)3 cover cells which are irregular to rectangular in shape and cover about half the sporangium, later becoming more elongate but rarely dividing.

Distribution. Rottnest I., W. Aust., to West I., S.Aust.

Habitat. D. baldockii occurs in the sublittoral, on limestone or wooden jetty piles, 1–25 m deep, only known from late spring and early summer.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 436–438 (1998)]