Metagoniolithon chara (Lam.) Ducker

Scientific Description

Habit and structure. Thallus medium red-brown to grey-red, 2–5 cm high, loosely to densely tufted, much branched with mainly synchronous production of even-length intergenicula and resultant even-topped outline, branching di- or trichotomous, occasionally more (–5). Intergenicula terete to slightly compressed, 2–3(–4) mm long and 400–600 µm in diameter, decreasing to 1–2 mm long and 200–300 µm in diameter above, in larger plants to 7 mm long below and 700–1000 µm in diameter; genicula untiered; apices with a mucilaginous cap 25–75 µm thick. Holdfasts 0.5–2 mm across, each with one to several fronds; epiphytic on stems of Amphibolis or some larger algae. Structure. Intergenicula of numerous arched medullary tiers 45–70 µm long, cells 9–15 µm in diameter with frequent lateral cell-fusions. Genicula 180–400 µm long. Apical cells slightly separate, without epithallial cells. Cortex present in both intergenicula and genicula, of short splaying to anticlinal filaments (5–)7–11 µm in diameter, with short epithallial cells and scattered hairs. Rhodoplasts discoid.

Reproduction. Conceptacles uniporate, borne on the surface of the intergenicula. Gametangial thalli dioecious. Carposporangial conceptacles 400–600(–800) µm in external diameter, each with a thin fusion cell bearing marginally up to 15 carposporangia terminating short filaments, more or less ovoid and 50–90 µm in diameter. Male conceptacles low, 600–800 µm in external diameter, with spermatangia on initials over the chamber floor, ovoid, 1–2 µm in diameter. Tetrasporangial conceptacles hemispherical, 600–750 µm in external diameter, each with a ring of 8–11 ovoid tetrasporangia, each 120–200 µm long and 45–110 µm in diameter, zonately divided.

Distribution.Port Denison, W. Aust., to Walkerville, Vic., and on King I., Bass Strait, mainly on Amphibolis. N.S.W.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 321–323 (1996)]