Dasya quadrispora Parsons & Womersley

Scientific Description

Habit and structure. Thallus medium to dark red-brown, 10–30 cm high, slightly mucilaginous, with several much branched axes and laterals, pyramidal to spreading in outline, terminal pseudolateral tufts dense and fairly prominent, denuded below. Axes and branches spirally branched from each segment, 1–2 mm in diameter below; lateral branches 0.5–1 mm in diameter, lesser branches 1.5–5 mm long and basally 100–200 µm in diameter, mostly ecorticate. Holdfast discoid, 1–3 mm across; epilithic. Structure. Pericentral cells 5, becoming corticate from several segments below branch apices, first by filaments of elongate cells lying between the pericentral cells, densely corticated below with the pericentral cells without surrounding rhizoids and remaining clear in section. Lateral branches arising from the basal cells of pseudolaterals. Pseudolaterals one per segment, spirally arranged, 0.5–1 mm long with 3–5 subdichotomies usually every 1(–2) cell below, upper filaments slender and unbranched; subdichotomies with joint walls basally adherent; basal and next cells 35–90(–130) µm in diameter and L/D (1–)1.5–2.5, usually tapering evenly and markedly to slender upper cells (often lost) 4–6 µm in diameter and L/D 8–15, ends rounded. Adventitious filaments absent; adventitious branches occasional. Rhodoplasts discoid to elongate, becoming ribbon like or in chains.

Reproduction. Gametophytes dioecious. Procarps not observed. Carposporophytes with a prominent fusion cell and basal nutritive cells, gonimoblast much branched with terminal rows of ovoid carposporangia 15–25 µm in diameter. Cystocarps urceolate with a globose base 0.5–1.2 mm across and a neck 100–250 µm long, sessile on lesser branches; pericarp 3–4 cells thick, outer cells ovoid, irregular. Spermatangial branches on mid cells of pseudolaterals, lanceoid to cylindrical, 120–250 µm long and 35–65 µm in diameter with 8–12 fertile segments, with a single pedicel and 1–2 apical cells. Tetrasporangial stichidia on lower cells of pseudolaterals, cylindrical and tapering above, on a 1–2-celled pedicel, 200–600 µm long and 80–140 µm in diameter, with 5–8 fertile segments each with 4 pericentral cells and subspherical tetrasporangia 30–50 µm in diameter, tetrahedrally divided, each with 3 ovoid cover cells.

Distribution. Hopetoun, W. Aust., to N Tas.

[After Parsons & Womersley in Womersley, Mar. Benthic Fl. Southern Australia IIIC: 462–465 (1998)]