Beard’s Provinces: South-West Province.
IBRA Regions: Swan Coastal Plain.
IBRA Subregions: Perth.
IMCRA Regions: Central West Coast, Leeuwin-Naturaliste.
Local Government Areas (LGAs): Capel, Cockburn, Cottesloe, Greater Geraldton, Rockingham.
Habit and structure. Thallus grey-red to purple, 4–15(–40) cm high, with one to several main pyramidal fronds, axes densely and irregularly radially branched for 3–4 orders, often denuded below; axes 1–3.5 mm in diameter, laterals 0.5–1.5 mm and lesser branches 0.2–0.5 mm in diameter, all basally constricted and tapering to rounded apices, terete to slightly compressed; diaphragms distinct in lesser branches, obscured in older parts, (0.5–)1–1.5(–2) mm apart, branches constricted at diaphragms except when old. Holdfast discoid, 1–4 mm across, becoming stoloniferous; epilithic or on Amphibolis (rarely Posidonia). Structure multiaxial with a ring of initials, developing a cortex of large inner cells (20–)25–40(–60) µm across, cutting off small outer cells which become continuous on older parts and 2–4 cells thick near the thallus base; longitudinal filaments peripheral only, usually with two complete cells (each with a secretory cell) and two part cells between the diaphragms; diaphragms monostromatic. Rhodoplasts discoid, in chains or ribbon like in inner cells.
Reproduction. Gametangial thalli dioecious. Carpogonial branches 4-celled, borne on inner cortical supporting cells together with a 2-celled auxiliary cell branch. Carposporophyte erect, with a basal fusion cell and branched gonimoblast filaments with terminal ovoid to angular carposporangia 30–55 µm in diameter. Cystocarps scattered, external, subspherical to urceolate and basally constricted, 0.7–1.3 mm in diameter; pericarp (40–)90–180 µm and (4–)6–10 cells thick, inner cells stellate and separating, ostiolate. Spermatangia in sori, spreading from near the diaphragms, cut off from chains of initials on outer cortical cells, ovoid, 3–5 µm in diameter. Tetrasporangia scattered, transformed from inner cortical cells, 60–80 µm in diameter, tetrahedrally divided.
Distribution. Rottnest I., W. Aust., to Western Port, Vic., and around Tas. New Zealand.
[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 125–127 (1996)]
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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/