- Reference
- Mar.Benth.Fl.S.Australia 286 (2003)
- Conservation Code
- Not threatened
- Naturalised Status
- Native to Western Australia
- Name Status
- Current
Scientific Description
Habit and structure. Thallus medium to dark red, erect, 5–40 cm high, with a terete to slightly compressed main axis, 2–4 mm in diameter, bearing similar main lateral branches irregularly, 5–15 cm long, all with radial and irregularly positioned (but often clustered and appearing somewhat umbellate), more or less determinate, branched laterals 2–8 cm long and 600–900 µm in diameter, bearing trichoblasts; axes denuded below. Holdfast discoid, 2–6 mm across; epilithic. Structure. Apices tapering, apical cell dome-shaped, thick walled, 25–35 µm in diameter, axial cells cutting off 4 pericentral cells, rapidly corticated and older branches with abundant rhizoidal filaments forming a largely rhizoidal medulla with the pericentral cells obscured, and a small-celled cortex. Trichoblasts produced apically from each segment, 600–900 µm long, basally branched from usually every second cell, basal walls adherent, lower cells 40–80 µm in diameter and L/D 1–1.5, rhodoplastic. Cells probably uninucleate; rhodoplasts discoid, chained in larger cells.
Reproduction. Gametophytes dioecious. Procarps on a lower cell of trichoblasts, with the supporting cell bearing a 4-celled carpogonial branch and a sterile group of 3 cells, rapidly pericarpic. Carposporophytes with a basal fusion cell and short, branched, gonimoblast with clavate terminal carposporangia 90–150 µm in diameter. Cystocarps stalked, ovoid, 1–2 mm in diameter; pericarp ostiolate, corticated, 5–7 cells thick. Spermatangial organs on branches of trichoblasts, 90–120 µm in diameter and L/D (2–)3–5, with 4 pericentral cells and 4–8 fertile segments, with a sterile apex 2–4 cells long. Tetrasporangia borne in simple or branched, corticated, determinate laterals bearing trichoblasts, spirally arranged, single per tier, borne adaxially (upwards) from the 4 pericentral cells, 180–320 µm in diameter.
Distribution.Eyre, W. Aust., to Cape Patterson, Vic.
Habitat. H. umbellifera is common in the drift in S. Aust., and western Vic., and has been collected in situ from 3 to 35 m deep.
[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 286–288 (2003)]