IMCRA Regions: WA South Coast.
Local Government Areas (LGAs): Esperance.
Habit and structure. Thallus dark-red to red-purple, 5–15(–20) cm high, densely tufted, axes (1–)2–3 mm broad, with numerous branches for 2–4 orders, irregular, sub-opposite or verticillate. Branches terete to slightly compressed, (0.5–)1–1.25 mm broad, linear to slightly curved, basally constricted, apices rounded; diaphragms 0.5–1(–1.5) mm apart, regular and conspicuous in surface view. Holdfasts small, discoid, on stoloniferous basal branches; epilithic or on Posidonia. Structure multiaxial with central and peripheral initials, developing a single-layered cortex of compact, polygonal cells 25–40 µm across with small cells cut off in the outer corners, and in older parts an inner cortex of rhizoidal filaments several filaments thick, derived from the peripheral diaphragm cells; longitudinal filaments both peripheral and central with one complete and two part cells between the diaphragms, the central cell bearing a secretory cell; diaphragms monostromatic. Rhodoplasts discoid, in chains.
Reproduction. Gametangial thalli probably dioecious. Carpogonial branches 4-celled, auxiliary cell branches 2-celled, borne on a cortical supporting cell with adjacent cortical cells proliferating. Carposporophyte with a basal branched fusion cell and branched gonimoblast filaments bearing ovoid to angular, terminal to subterminal carposporangia 45–60 µm in diameter; basal nutritive tissue slight, erect filaments slender, cells stellate, conspicuous when young. Cystocarps scattered, external, globular to urceolate, 0.5–1 mm in diameter. Pericarp 180–280 µm and 4–6 cells thick, inner cells stellate with long arms, ostiolate. Spermatangia not observed. Tetrasporangia scattered, transformed from cortical cells, 60–90(–120) µm in diameter, tetrahedrally divided.
Distribution. Rottnest I., W. Aust., to Jervis Bay, N.S.W., and around Tas.
[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 121–123 (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/