Griffithsia pulvinata Baldock

Scientific Description

Habit and structure. Thallus medium to dark red, 1–3 cm high, filaments erect, subdichotomous several times, ecorticate, forming dense pulvinate masses. Attached at the base by anastomosing rhizoids; epilithic. Structure. Cells globose near the thallus apex and 750–900(–1200) µm in diameter, in mid and basal thallus clavate to obovoid, 1–2(–2.1) mm in diameter and L/D 2–3.

Reproduction. Gametophytes dioecious. Female axis 3-celled, subapical but displaced laterally by continued growth of the vegetative apical cell, flanked by a pair of hair-like synchronic laterals. Procarp systems subapical, each with a sterile lateral cell, and supporting cell bearing a sterile cell apically and a lateral, recurved carpogonial branch of 4 cells. The inner of two connecting cells, cut off from the carpogonium after fertilisation, fuses with the supporting cell, which cuts off an apical auxiliary cell; post-fertilisation fusion cell columnar, bearing 1–3 gonimolobes terminally, most cells of which become ovoid carposporangia 25–30 µm in diameter; hypogenous cell producing abaxially 9–12(–14) 2-celled involucral branches, of which the larger, incurved apical cells are occasionally furcate, 325–350 µm in diameter and L/D 1.8–2. Growth of the vegetative axis is often arrested during procarp development, and 1(–4) vegetative laterals arise from the vegetative subapical cell, displacing the carposporophyte to an apparently terminal position. Spermatangia borne on numerous, minute fascicles from the subapical cell and occasionally the cell below, clustered in the constrictions between the cells; involucre absent. A fascicle is at first polychotomous, but elongation of some cells establishes an axis of 3–4 terete cells bearing 1–4 polychotomous branches, the end cells of which each produce 1–2 spermatangia. Tetrasporangia borne in cell constrictions on numerous minute fascicles 1–3 times di- or trichotomous with small, terete cells, each of which produces a whorl of 1–6 lachrimiform tetrasporangia, 55–88 µm in diameter, or a 1-celled involucral branch equal in size to a tetrasporangium. The sterile involucral cells stain lightly, in contrast to sporangia, which stain densely and divide when quite small.

Distribution.Streaky Bay, S. Aust., to Port Phillip Heads, Vic.

Habitat. G. pulvinata is common in small, low, cushion-shaped masses on rock in the upper sublittoral to lower eulittoral, usually in shaded positions.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 324 (1998)]