Habit and structure. Thallus medium red to grey-red, mucilaginous, (3–)6–10(–20) cm high, pyramidal in outline, with one or a few percurrent axes bearing irregularly radially laterals for 2–3 orders. Main axes terete to slightly compressed, 1–3 mm broad, laterals terete, 1–2 mm broad, ultimate branchlets clavate, 0.5–1 mm broad, apices rounded, bases constricted. Holdfast discoid, 1–3 mm across, with several fronds; epiphytic on various algae or epilithic. Structure multiaxial, with a cluster of apical cells producing a cortex of a single layer of large inner cells 30–80 µm across and an outer cortex 1–2 cells thick, outer cells ovoid and 5–10 µm in diameter, with a medulla of a network of branched filaments (5–10 µm broad) adjacent to the cortex, with some cells bearing ovoid secretory cells 10–20 µm in diameter. Constrictions pseudoparenchymatous, 220–320 µm long, with filaments on each side. Rhodoplasts discoid, in chains in inner cells.
Reproduction. Gametangial thalli dioecious. Carpogonial branches 3-celled, borne on inner cortical cells near branch apices, with 2-celled auxiliary cell branches. Carposporophyte with basal partly fused cells and all upper cells forming lobes of ovoid carposporangia 40–60 µm in diameter, surrounded by an involucre of lax erect filaments from the auxiliary cell initial; cystocarps immersed in the branchlet, 500–650 µm in diameter, with a small ostiole formed by cortical proliferation. Spermatangia unknown. Tetrasporangia in scattered, depressed, sori 120–180 µm across, and 180–200 µm deep, cut off laterally from cells lining the depression, (50–)75–110 µm in diameter, tetrahedrally divided.
Distribution. Yanchep, W. Aust., to Western Port, Vic.
[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 142–144 (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/