Anotrichium elongatum (Harv.) Baldock

Scientific Description

Habit and structure. Thallus variable, soft in texture, light red to dark red, subdichotomous with dense or lax branching or in spreading tufts or with lateral tufts arising irregularly or somewhat regularly from main axes, 2–30 cm high, filaments twisted together or loosely entwined with decurrent rhizoids. Attached by basal rhizoids; epilithic or epiphytic mainly on seagrasses. Structure. Cells cylindrical, variable in size, near the thallus apex 48–60 µm in diameter and L/D 6–8, in mid thallus 220–250 µm in diameter and L/D 3–6, near the thallus base 260–300 µm in diameter and L/D 2–5; filaments gradually attenuate towards apices.

Reproduction. Gametophytes dioecious. Female axes 3-celled, subapical, displaced laterally by continued growth of the vegetative cell, flanked by 2 caducous synchronic, hair-like laterals; procarp systems subapical, each with an abaxial sterile cell and an adaxial supporting cell bearing a sterile cell apically and a recurved, 4-celled carpogonial branch laterally; hypogenous cell enlarging, becoming pyriform, 160–240 µm in diameter and L/D 1–2 and producing 1(–2) whorls of 6–11, elongate, one-celled synchronic involucral branches 55–95 µm in diameter and L/D 4–6, incurved about the developing gonimoblast; fusion cell columnar, bearing 1–3 gonimolobes terminally, most cells of which become globose carposporangia, 20–40 µm in diameter. Carposporophyte 250–460 µm across. Spermatangia borne in solitary heads, initially ovoid, becoming cylindrical, 180–250 µm in diameter and L/D 1.8–2, on clavate pedicels 70–90 µm in diameter and L/D 1.5–1.8, single and adaxial from the upper ends of many cells near the thallus apex; each head with 3 elongate axial cells each bearing 4–6 periaxial cells dividing polychotomously several times, the ultimate cells producing spermatia apically. Tetrasporangia single, terminal on clavate pedicels 35–45 µm in diameter and L/D 1–1.5, produced successively in groups of 3–7 from the upper, adaxial shoulder of most cells near the thallus apex, globose, 70–85 µm in diameter, tetrahedrally divided.

Distribution.Recherche Archipelago, W. Aust., to Western Port, Vic., and around Tas.

Habitat. A common species from the lower eulittoral to 38 m deep.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 352–354 (1998)]