Austroclonium charoides (Harv.) Min-Thein & Womersley

Scientific Description

Habit and structure. Thallus erect and spreading, soft, medium to dark red to red-brown, 5–15 cm high, much branched mainly verticillately for 4–5 orders, segments terete but narrowing to base and apex, mostly 0.5–1(–1.5) cm long and 0.5–1 mm in diameter, shorter above, with frequent small proliferations and some branches extended into long, terminally hooked tendrils. Holdfast originally discoid, later with attachment mainly by the tendrils; epiphytic on seagrasses and larger algae. Structure uniaxial with each axial cell producing two periaxial cells usually at right angles and alternating, developing a medulla of elongate periaxial cells and rhizoids around the persistent axial filament, and a cortex 1–2 cells thick with slight rosettes of small outer cells. Rhodoplasts discoid, numerous per cell.

Reproduction. Sexual thalli dioecious; procarpic. Carpogonial branches 3-celled, borne on a cell of a periaxial filament within the cortex, orientated laterally with reflexed trichogyne. Auxiliary cell next outwards from the supporting cell, becoming darkly staining along with adjacent cortical cells, without nutritive tissue; gonimoblast initial produced laterally or inwardly, forming a compact group of cells. Carposporophyte with a small fusion cell, connecting back through the periaxial filament, and branched gonimoblast filaments directed mainly inwards, terminating in chains of 2–3 ovoid carposporangia 30–40 µm in diameter, surrounded by lax filamentous enveloping tissue. Cystocarps swelling branchlets, 200–300 µm across, with a slight pericarp of cortical cells, ostiolate. Spermatangia in scattered clusters, derived via initials from outer cortical cells. Tetrasporangia pit-connected laterally to outer medullary cells, extending through the cortex and medulla, ovoid, 27–45 µm in diameter, zonately divided.

Distribution. Elliston, S. Aust., to Wilsons Promontory, Vic.

Habitat. A. charoides occurs in moderately deep-water, epiphytic on seagrasses and some larger algae under moderate water movement.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 433–435 (1994)]