Echinothamnion hystrix (Hook.f. & Harv.) Kylin

Scientific Description

Habit and structure. Thallus dark brown-red, erect, 10–35 cm high, moderately branched with long, terete, heavily corticated main indeterminate branches bearing irregularly radial indeterminate laterals, all branches clothed with short tufts of ecorticate determinate laterals 1–2(–3) mm long. Axes often denuded basally, 1–2 mm in diameter below, tapering gradually to 0.2–0.4 mm in diameter near apices. Holdfast fibrous 0.5–2 cm across; epilithic or epiphytic. Structure. Apical cells of indeterminate branches dome-shaped, 8–10 µm in diameter, with 4 pericentral cells and producing spirally arranged determinate branches close to apices. Cortication commencing close to apices (especially in rough-water plants) with the pericentral cells remaining conspicuous in transverse section, outer cortical cells irregular in shape, mostly L/D 1–2. Determinate laterals first simple (remaining so near base of some plants), soon branched from near the base of their primary branch; lesser branches 0.5–1.5 mm long, 60–120 µm in diameter and tapering near their apices, segments L/D 1–2(–2.5). Trichoblasts mainly on lateral branches of determinate laterals, 0.5–1 mm long, branched, soon caducous. Cells probably uninucleate; rhodoplasts discoid to elongate, becoming chained.

Reproduction. Gametophytes dioecious. Procarps on trichoblasts on young laterals of determinate branches, with a supporting cell bearing a 4-celled carpogonial branch surrounded by a pre-fertilization pericarp. Carposporophytes with a small basal fusion cell and short gonimoblast filaments bearing clavate terminal carposporangia 30–40 µm in diameter. Cystocarps sessile, slightly urceolate with a short neck, 500–750 µm in diameter; pericarp ostiolate, 2 cells thick, outer cells isodiametric, angular. Spermatangial branches on basal branches of trichoblasts, ovoid, 50–90 µm long and 30–45 µm in diameter, no sterile apical cell. Tetrasporangia in lateral branches of determinate branches, single per segment, spirally arranged and bulging the branch, 50–75 µm in diameter.

Distribution.Nichol Bay, W. Aust., to Walkerville, Vic., and around Tas. New Zealand (?).

Habitat. E. hystrix is a common species, varying considerably in robustness. Plants from sheltered habitats are generally slender, those from rough-water coasts usually relatively robust.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 222–224 (2003)]