Herposiphonia rostrata (Sond.) Reinbold

Scientific Description

Habit and structure. Thallus medium red, with prostrate axes producing erect axes 2–6 cm high, bearing laterally relatively short indeterminate axes with simple determinate laterals mostly pectinately and abaxially arranged, the indeterminate laterals separated by usually 3 segments bearing determinate laterals. Attachment by rhizoids; epiphytic, on Amphibolis and various algae. Structure. Apices revolute with determinate laterals on the convex side, apical cells hemispherical, 12–15 µm in diameter. Pericentral cells 12–14 in axes, (10–)11(–12) in determinate laterals; axes (250–)300–450 µm in diameter, segments L/D 0.5–0.8, determinate laterals 1.0–2.5 mm long, 100–150 µm in diameter, segments L/D 0.8–1.2. Trichoblasts on upper segments of determinate laterals, 200–1000 µm long, basal cells 10–20 µm in diameter and L/D 1–2. Rhizoids cut off from pericentral cells, unicellular with digitate haptera. Cells uni- to multinucleate; rhodoplasts discoid to elongate.

Reproduction. Gametophytes dioecious. Procarps not observed. Carposporophytes with an inconspicuous basal fusion cell and short gonimoblast with clavate terminal carposporangia 30–60 µm in diameter. Cystocarps ovoid, 300–900 µm in diameter; pericarp ostiolate, 2 cells thick, ecorticate, outer cells isodiametric, irregular in shape. Spermatangial branches replacing trichoblasts or basal branches thereof, 100–330 µm long and 40–80 µm in diameter, with 1–2 sterile basal cells and a sterile apical filament of 2-several cells. Tetrasporangia in straight or curved series of 2–6 in determinate laterals, 70–130 µm in diameter, with 2–3 cover cells, swelling the segments to 150–220 µm in diameter.

Distribution. Yanchep, W. Aust., to Westernport Bay, Vic.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 295 (2003)]