- Reference
- Remarques sur les Sphacelarialees 386-393 (1904)
- Conservation Code
- Not threatened
- Naturalised Status
- Native to Western Australia
- Name Status
- Current
Scientific Description
Habit and structure. Thallus medium to dark brown, 4–12(–20) cm long, with a rhizoidal holdfast 2–8 mm across and numerous, erect, pinnately much branched axes, often basally denuded; epilithic or on Amphiholis. Branching of 3–4 orders, usually regularly alternately distichous with laterals every (2–)3–6(–12) segments with lesser laterals determinate and tapering to small apical cells;lower and mid axes producing descending rhizoids which corticate the axes and form the basal holdfast; phaeophycean hairs absent. Axes 120–160(–190) µm in diameter with segments L/B0.5–1.0, corticated by small, rectangular cells in rows of 2–4, and rhizoids below; primary laterals 70–90 µmin diameter with segments L/B(0.4–)0.5–0.8(–1.0); ultimate laterals 50–90 µmin diameter near their bases with segments L/B0.4–0.8; rhizoids arising from pericysts; adventitious branchlets absent.
Reproduction. Unilocular sporangia densely clustered, formed in axillary groups on distichous (or slightly irregular) laterals, borne on simple or branched, 2–4(–10) celled, straight to slightly curved pedicels, subspherical to slightly ovoid, (25–)30–45 µmin diameter. Sexual plants with oogonia and antheridia borne in mixed clusters of 2–6 in axils of laterals, each with a 2–4 celled pedicel; oogonia subspherical, 65–90 µmin diameter; antheridia subspherical to ovoid, 60–70 µm in diameter.
Distrihution.From Eucla, W. Aust., to Cape Northumberland, S. Aust. (and Hobsons Bay, Vic.?), and the N coast of Tas.
Habitat. H. ramulosa is not uncommon in the Gulf St Vincent region of S. Aust., and appears to be confined to regions of moderate water movement or to deeper water. It has been collected at 15 to 48 m depths off Cape Northumberland and West Island.
[After Womersley, Mar. Benthic Fl. Southern Australia II: 172–174 (1987)]