Beard’s Provinces: Eremaean Province, Northern Province, South-West Province.
IBRA Regions: Carnarvon, Dampierland, Jarrah Forest, Pilbara, Swan Coastal Plain, Warren, Yalgoo.
IBRA Subregions: Cape Range, Edel, Perth, Pindanland, Roebourne, Southern Jarrah Forest, Warren, Wooramel.
IMCRA Regions: Abrolhos Islands, Central West Coast, Kimberley, Leeuwin-Naturaliste, Ningaloo, Pilbara (nearshore), Pilbara (offshore), Shark Bay.
Local Government Areas (LGAs): Ashburton, Augusta Margaret River, Broome, Busselton, Carnarvon, Cockburn, Cocos Islands, Coorow, Cottesloe, Dandaragan, Derby/west Kimberley, Exmouth, Greater Geraldton, Irwin, Karratha, Mandurah, Mosman Park, Murray, Peppermint Grove, Port Hedland, Rockingham, Shark Bay, Stirling, Wanneroo, Wyndham-East Kimberley.
Habit and structure. Thallus medium to dark brown, (10–)20–40 cm long, with a short, terete, stipe bearing few to many primary branches, each irregularly tristichously and spirally branched from the rhachis, with most laterals of more-or-less limited growth. Holdfast discoid-conical, 5–10 mm across; epilithic. Primary branches with triquetrously arranged wings, each 0.5–2(–3) cm long and 1–5(–7) mm broad above before terminating, with vesicles developing centrally within the medulla in the upper part of the branches; lower part of branches usually denuded; vesicles elongate, 5–10 mm long and 2–4 mm in diameter. Lesser branches (1–)2–6(–10) cm long, compressed to triquetrous, with marginal rows of short teeth 0.5–2(–3) mm long, cryptostomata numerous, scattered. Growth from a single, three-sided, apical cell in an apical depression. Structure of a central medulla of compact, elongate, cells and an extensive cortex of isodiametric cells decreasing in size to the surface phaeoplastic meristoderm; medulla absent or slight in the wings; vesicles with longitudinal strands of smaller cells opposite the wings.
Reproduction. Thalli monoecious. Conceptacles bisexual, scattered over the thallus without distinctive receptacles; oogonia sessile, ovoid and broad based, 80–120 µm long and 35–60 µm in diameter; antheridia sessile or on short, branched, paraphyses, elongate-ovoid, 20–30 µm long and 8–12 µm in diameter; simple paraphyses also present.
Distribution. From the tropics to Augusta, W. Aust., Port Broughton and Port Augusta, S. Aust., and the tropics south to Port Stephenss, N.S.W. In southern Australia, known from the Port Broughton region and Port Augusta in northern Spencer Gulf, S. Aust.
[After Womersley, Mar. Benthic Fl. Southern Australia II: 356 (1987) as Hormophysa triquetra ]
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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/