Spyridia dasyoides Sond.

Scientific Description

Habit and structure. Thallus dark red to red-brown, usually 10–20 cm high, erect, much branched irregularly to subdistichously with one to several axes; axes and larger branches heavily corticated, terete to angular and becoming four-sided with thickened cortical flanges in line with the 4 ranks of ramelli, densely branched. Axes 1–2(–2.5) mm in diameter, often denuded but sometimes with numerous, short, proliferous branches, tapering to 0.5–0.8 mm in diameter with lesser branches 0.2–0.5 mm in diameter; laterals arising from nodal cells. Holdfast discoid, soon becoming fibrous and stoloniferous; epilithic or epiphytic. Structure. Segments largely obscured by cortication, L/D 0.5–1, with 8 periaxial cells producing 16 internodal cells and the 8 cells soon with interposed rhizoidal cells giving both nodal and internodal rings of 16 cells; cortication commencing within a few segments of apices, of elongate cells and later appearing pseudoparenchymatous, a few cells thick on lesser branches, many (especially on flanges) cells thick on axes. Ramelli arising from an enlarged periaxial cell, in opposite and more or less decussate pairs on successive segments (often displaced to two rows on each side in the plane of branching), (1–)1.5–2(–2.5) mm and (16–)8–22 cells long, relatively uniform in diameter but tapering fairly abruptly to a point, (70–)100–150 µm in basal diameter, cells L/D about 1(–1.5). Ramelli with 16–20 nodal cells, each cutting off 1–2 cells (which often divide again) on both sides (anteriorly first), producing a nodal band (2–)3–4(–6) cells broad. Cells uninucleate; rhodoplasts discoid to elongate.

Reproduction. Gametophytes dioecious. Female axes with alternating sterile and procarpic segments, the latter with a 4-celled carpogonial branch on the supporting cell and usually two other periaxial cells. The mature carposporophyte is short-stalked, irregularly globular to bilobed, 400–600 µm across, with two or three discrete lobes and the pericarp is relatively firm at its periphery. Spermatangia cover the lower (except basal) several segments of young ramelli of adventitious branchlets lying between older ramelli, forming male organs 120–200 µm in diameter. Tetrasporangia sessile, 1–3 per cell, mostly on the upper (adaxial) side of the ramelli, subspherical, 50–90 µm in diameter, tetrahedrally divided.

Distribution. Port Denison, W. Aust., to Gabo I., Vic and N.S.W.

Habitat. S. dasyoides usually occurs on rough-water coasts from low tide level to depths of 33 m.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 379–381 (1998)]