Beard’s Provinces: South-West Province.
IBRA Regions: Swan Coastal Plain.
IBRA Subregions: Perth.
IMCRA Regions: Abrolhos Islands, Central West Coast, Leeuwin-Naturaliste, WA South Coast.
Local Government Areas (LGAs): Albany, Cockburn, Esperance, Greater Geraldton, Rockingham.
Habit and stucture. Thallus medium to dark brown, membranous, hollow and irregularly inflated to bullose, (3–)10–70(–100) cm long and (1– )2–8(–12) cm in diameter, with a small holdfast 0.5–2 mm across, and a short, slender stipe 2–10 mm long, expanding suddenly to the inflated thallus; usually epiphytic on Posidonia. Structure of membrane 120–240(–300) µm and 3–5 cells thick, with a cortex of small phaeoplastic cells, several overlying each of the larger medullary cells; cortical cells more or less in rows, angular, isodiametric, 20–35 µm across in surface view, each with several discoid phaeoplasts with 1–2 pyrenoids. Phaeophycean hairs single or in small groups, 16–20 µm in diameter.
Microthallus (unknown in Australia) filamentous, branched.
Reproduction. Sori of sporangia rounded to elongate, scattered moderately densely, 100–350 µm across, containing sessile, pyriform to clavate, unilocular sporangia 30–40 µm long and 20–30 µm in diameter, and sessile, ovoid, plurilocular sporangia (usually in the same sorus) 40–60 µm long and 30–40 µm in diameter, together with a few phaeophycean hairs and clavate paraphyses 2(–4) cells long, the end cell 20–25 µm in diameter with dense physodes.
Microthalli with plurilocular gametangia producing isogametes; or reproducing the macrothallus directly from zooids from unilocular sporangia.
Distribution. In western and southern Australia, from the Houtman Abrolhos Is., W. Aust., to Pittwater, N.S.W., and the N and E coasts of Tas.
Habitat. Epiphytic on Posidonia and Amphibolis usually in shallow, sheltered waters but extending to 22 m deep.
[After Womersley, Mar. Benthic Fl. Southern Australia II: 320–322 (1987)]
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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/