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- Reference
- J.Bot.(Morot) 287 (1897)
- Conservation Code
- Not threatened
- Naturalised Status
- Native to Western Australia
- Name Status
- Not Current
Scientific Description
Habit and structure. Thallus dark red-brown, forming dense tufts or turfs 2–4(–6) cm high with numerous erect axes from prostrate, branched, filaments; erect axes simple or occasionally branched, with pinnate, alternate, determinate laterals, the axis linear in outline and 2–3 mm broad, the laterals simple, 1–2 mm long; attachment by rhizoids from prostrate filaments; epilithic. Structure. All axes and laterals ecorticate. Prostrate filaments terete, 120–160 µm in diameter with segments L/D 0.8–1.4(–2), branching 2–4 segments apart, with 7–8 pericentral cells; rhizoids unicellular, cut off from pericentral cells, with multicellular discoid haptera. Erect axes slightly compressed, 180–230 µm broad, segments L/D 0.8–1.2, with 8–10 pericentral cells, 5–6 visible in side view. Determinate laterals straight or incurved when young, linear and tapering apically to a small apical cell, coalesced with axes over 1–1.5(–2) segments, 16–25 segments long, segments L/D (0.3–)1–1.5. Trichoblasts usually absent, Cells uninucleate; rhodoplasts discoid.
Reproduction. Gametophytes dioecious; one case of mixed phases (male on tetrasporophyte) known. Procarps probably borne on short trichoblasts, segments soon polysiphonous. Carposporophyte with a small basal fusion cell, short gonimoblast filaments and clavate terminal carposporangia 30–45 µm in diameter. Cystocarps ovoid, short-stalked, 300–800 µm in diameter; pericarp ostiolate, ecorticate, 2 cells thick, outer cells isodiametric. Spermatangial organs near apex of axes, elongate-ovoid to clavate and often curved, 45–120 µm in diameter and 130–350 µm long, with 1–2 sterile basal and apical cells. Tetrasporangia indeterminate laterals in straight rows in 6–10 successive segments, subspherical to slightly ovoid, 35–60 µm in diameter, with 2 elongate cover cells.
Distribution.Widely distributed in Atlantic and Pacific Oceans. In southern Australia, from Bunbury, W. Aust., to Byron Bay, N.S.W. and Taroona, Tas.
Habitat. P. pennata forms mats or turfs close to low tide level under moderate wave action, rarely in deep water.
[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 338–340 (2003)]