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Heterothamnion platythaliae Athanas.

Opera Bot. 186-188, figs 95-97 (1996)
Conservation Code
Not threatened
Naturalised Status
Native to Western Australia
Name Status

Scientific Description

Habit and structure. Thallus in dense spreading tufts 3–5 mm high, with numerous erect axes, each axial cell bearing (1–)2 whorl-branchlets. Attachment by rhizoids from erect axes, penetrating the host edges, probably at conceptacles; epiphytic on Platythalia angustifolia. Structure. Apical cells 12–16 µm in diameter and L/D 1–1.5, enlarging rapidly to axial cells 50–80 µm in diameter and L/D 1.5–2.7, tapering and with shorter cells near the base. Whorl-branchlets one or two per axial cell, if two situated usually at right angles and alternating on successive cells, with one of the 2 often more branched than the other and with 2–4 branches from the basal or upper cells; whorl-branchlets 200–500 µm and 6–10 cells long, basal cells slightly longer than the next outer cell, 25–40 µm in diameter and L/D 1.2–1.6(–2), tapering to terminal cells 12–22 µm in diameter and L/D 1–1.5, ends rounded; gland cells apparently absent. Lateral branches borne on the basal cell of whorl-branchlets. Cells probably uninucleate; rhodoplasts discoid.

Reproduction. Gametophytes probably monoecious. Carpogonial branches borne on the basal cells of reduced 2-celled whorl-branchlets which may continue growth. Carposporophytes terminal, surrounded by 4 whorl-branchlets, with rounded gonimolobes 100–200 µm across of ovoid carposporangia 20–25 µm in diameter. Spermatangia on small branched clusters on the adaxial side of lower cells of whorl-branchlets shortly below the carposporophytes. Tetrasporangia borne on lower cells of whorl-branchlets, sessile, subspherical, 30–40 µm in diameter, tetrahedrally divided.

Distribution.Known only from Sarge Bay, Cape Leeuwin, W. Aust., on drift Platythalia angustifolia.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 162–166 (1998)]

John Huisman & Cheryl Parker, 3 August 2021


IMCRA Regions
Local Government Areas (LGAs)
Augusta Margaret River.