Sarconema filiforme (Sond.) Kylin

Scientific Description

Habit and structure. Thallus dark red-brown, erect, 10–30 cm high, regularly subdichotomously branched at intervals of 1–3(–6) cm, branches firm, terete, 0.5–1(–1.5) mm in diameter, linear throughout. Holdfast discoid, 2–6 mm across, with several fronds becoming basally stoloniferous. Structure multiaxial, developing a medullary core of compact longitudinal filaments 8–14 µm in diameter and a broad cortex 10–12 cells across, inner cells ovoid to irregular, becoming thick walled, 20–60 µm across, decreasing to outer cortical cells 3–4 µm in diameter and L/D 1–2; hairs in small clusters in shallow pits. Rhodoplasts discoid, few per cell.

Reproduction. Carpogonial branches and auxiliary cells unknown. Carposporophytes with a central, lobed fusion cell with many arms producing short chains of irregular ovoid to clavate carposporangia 18–25 µm in diameter, with the subterminal sporangium usually less advanced than the terminal; enveloping tissue absent, but the cortex proliferating outside the carposporophyte and becoming ostiolate. Cystocarps often grouped, sunken but distinctly bulging the branch. Spermatangia unknown. Tetrasporangia scattered in the outer cortex, ovoid, 35–50 µm long and 20–25 µm in diameter, zonately divided.

Distribution.Indo-pacific tropics and subtropics. In Australia, south to Rockingham on the west coast, from Elliston, S. Aust., Sorrento, Vic., and from Jervis Bay, N.S.W. north on the east coast.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 344–345 (1994)]