Beard’s Provinces: South-West Province.
IBRA Regions: Jarrah Forest, Swan Coastal Plain.
IBRA Subregions: Perth, Southern Jarrah Forest.
IMCRA Regions: Central Victoria, Leeuwin-Naturaliste, WA South Coast.
Local Government Areas (LGAs): Albany, Cockburn.
Habit and structure. Thallus dark green, drying dark brown-green, sometimes light brown-green in lower eulittoral plants, forming dense spreading tufts to 15 cm high, with many stipes from a matted rhizoidal holdfast; filaments branched from almost every cell. Growth entirely acropetal with lateral branches arising usually from the subapical cell, and with one or commonly two (and then opposite) or occasionally three to five laterals (at acute angles) from each parent cell; cross walls at first steeply inclined to parent cell, less so in older parts. Basal and lower cells of stipes and older branches each producing a descending rhizoid which may branch and with annular constrictions; lower thallus cells often with annular constrictions over the lower 0.2–0.5 of their length. Apical cells cylindrical with rounded to slightly tapering tips, (70–)100–220 µm in diameter, L/B 3–13; ultimate branch cells (70–)100–220 µm in diameter, L/B 2.5–13; basal stipe cells slightly clavate, 350–420 µm in maximum diameter, L/B 5–22, sometimes tapering into a rhizoid; ratio of basal cell to apical cell diameters 1.5–3(–5 in plants with narrow apical cells); cell walls relatively thin near apex (3–6 µm), below 10–12 µm thick and 20–30 µm thick near base.
Reproduction. By zoospores only, produced in upper cells following intercalary cell division.
Distribution. Warm temperate Europe, Mediterranean, African and American tropics, Solomon I., New Zealand. In southern Australia, from Rottnest I., W. Aust., to Sorrento, Vic.
Habitat. In shallow pools on rough-water platforms and in the sublittoral.
[After van den Hoek & Womersley in Womersley, Mar. Benthic Fl. Southern Australia I: 193–194 (1984)]
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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/