Tiparraria aurata Womersley

Scientific Description

Habit and structure. Thallus orange-brown, (1–)2–3 cm high, largely free from the host, with prostrate filaments bearing from successive segments a long, branched, indeterminate lateral, a short, slightly developed, branched lateral, and no lateral on 1(–3) segments, this sequence (with slight variation) then repeated on the next 3 segments. Erect indeterminate laterals becoming branched apically (especially when fertile), 5–10(–20) mm long, branched usually from successive segments and each pair separated by 1–8 unbranched segments. Attachment by rhizoids; epiphytic on Posidonia and Amphibolis. Structure. Indeterminate apices upwardly recurved, apical cells hemispherical, 10–15 µm in diameter, segmenting transversely and subapical cells obliquely. Segments ecorticate, with (9–)11–13 pericentral cells, 200–300 µm in diameter and L/D 0.7–1.2 in axes and 150–250 µm in diameter in lesser branches with L/D 1–1.5. Branches of erect indeterminate laterals bearing prominent trichoblasts, much branched, 1–2 mm long, basal cells 80–100(–110) µm in diameter, short when immature, L/D 2–5 when mature. Rhizoids cut off from pericentral cells, unicellular with digitate haptera (becoming multicellular with ends of haptera branches cut off as terminal cells). Cells multinucleate; rhodoplasts discoid, becoming chained in older cells.

Reproduction. Gametophytes dioecious. Procarps not observed. Carposporophytes with a basal fusion cell and short gonimoblast with clavate terminal carposporangia 30–45 µm in diameter. Cystocarps short-stalked, ovoid, 350–750 µm in diameter; pericarp ostiolate, 2 cells thick, ecorticate, outer cells irregular, angular. Spermatangial organs replace usually the second cell of trichoblasts, 70–110 µm in diameter and L/D 1.5–2, with a sterile basal cell and 2 to several sterile apical cells. Tetrasporangia in upper branches of indeterminate laterals, spirally arranged, single per segment, 60–100 µm in diameter, with 3 cover cells.

Distribution.Cliff Head, W. Aust., to Kingston, S. Aust., and N Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 303 (2003)]