Protokuetzingia australasica (Mont.) Falkenb.

Scientific Description

Habit and structure. Thallus medium to dark red-brown, 5–15 cm high, spreading, oppositely but irregularly branched by loss of laterals, branches linear, compressed, endogenous, 0.5–1.5 mm broad, apices revolute, with a slight midrib, some axes with tendril-like ends. Holdfast discoid or tendril-like; epiphytic on Amphibolis or algae, or epilithic. Structure. Apical cell dome-shaped, 20–25 µm in diameter (including thick walls), cutting off 6 pericentral cells, 2 lateral, 2 dorsal and 2 ventral, with frequent abaxial trichoblasts from each segment near apices and occasionally on the margins. Cortex present from near apices, 2–3 cells broad on edges and 1–2 cells thick on faces of branches. Cells uni- or multinucleate; rhodoplasts discoid, chained in larger cells.

Reproduction. Gametophytes dioecious. Procarps on the lower cells of trichoblasts, with a 4-celled carpogonial branch, borne abaxially on short marginal or submarginal involute branchlets. Carposporophytes with a basal fusion cell and short, branched gonimoblast with clavate to obovoid terminal carposporangia. Cystocarps ovoid, short-stalked, 500–700 µm in diameter; pericarp ostiolate, 3–5 cells thick. Spermatangial organs on branches of trichoblasts borne on short lateral branchlets, globose to shortly ovoid, 180–220 µm in diameter, with 1(–3) sterile basal cells 30–50 µm in diameter and L/D 2–4. Tetrasporangial stichidia marginal or submarginal, in groups of 1–3, terminally involute, lanceolate, compressed, corticated, 0.9–1.6 mm long and 250–300 µm broad, with tetrasporangia paired, in two longitudinal rows, 80–120 µm in diameter; adaxial trichoblasts often present near apices of stichidia.

Distribution.Port Denison, W. Aust., to San Remo, Vic., and around Tas.

Habitat. P. australasica is not uncommon in shallow water on calm to rough-water coasts along most of southern Australia.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 374–376 (2003)]