IMCRA Regions: Central West Coast, Leeuwin-Naturaliste, WA South Coast.
Local Government Areas (LGAs): Augusta Margaret River, Cockburn, Dandaragan, Esperance.
Habit and structure. Thallus medium to dark red, (2–)5–15 cm long or broad, cartilaginous, more or less orbicular when young, becoming much divided into irregular, lacerate branches 5–15 mm broad with broader flabellate ends, (180–)250–450 µm thick, with more or less concentric growth zones and faint radial striae, epilithic and basally attached but most of the thallus largely free from the solid substrate. Structure. Basal-layer of radiating lines of cells, each cell 10–18 µm in diameter and L/D 2–4, producing from their lower side multicellular rhizoids with the first cell cylindrical and more or less at right angles to the basal-layer cell; hypobasal calcification present. Erect filaments assurgent at 35–45°, attached to the distal end of the basal-layer cells, 15–20 cells long, 8–12 µm in diameter with cells L/D (2–)3–4 below, branching from the lower 1–3 cells, erect above and 6–10(–12) µm in diameter with uppermost cells isodiametric to L/D 0.5; sideways growing filaments occasional to common in the lower to mid thallus; internal calcification absent.
Reproduction. Sexual plants dioecious, with slightly raised nemathecia. Female nemathecia 2–4 mm across, with slender paraphyses 240–320 µm and 10–15 cells long, with a firm, patterned, pellicle; carpogonial branches 3–4 cells long, borne on the same basal cell as 3–4-celled auxiliary cell branches; carposporangia in pairs, the pair ovoid, 45–65 µm in diameter and 80–145 µm long. Male nemathecia pale, 0.5–2 mm across, 80–120 µm high with a prominent pellicle, with very numerous, closely adjacent rows of 10–12 tiers each of 3–5 spermatia 2–3 µm across, without paraphyses. Tetrasporangial nemathecia raised, dark red, in scattered to more or less concentric patches 1–3(–6) mm across, paraphyses 160–320 µm and 10–15 cells long; tetrasporangia (120–)160–200 µm long and (80–)95–130 µm in diameter, decussately cruciately divided.
Distribution. New Zealand. Flat Rocks, S of Geraldton, W. Aust., around southern Australia to Coffs Harbour, N.S.W., and around Tas.
Habitat. P. novae-hollandiae is essentially a deep water species, know from shaded pools to 48 m deep.
[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 157–158 (1994)]
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/