Hymenocladia filiformis J.Agardh

Scientific Description

Habit and structure. Thallus 4–14 cm high, subdichotomously to laterally branched largely complanately, branches slightly compressed, 0.5–1 mm broad below, tapering slightly to 0.2–0.5 mm broad above, apices rounded. Holdfast discoid; epiphytic on Amphibolis. Structure multiaxial, with a cortex 2–3(–4) cells broad, outer cells ovoid and 2–3 µmin diameter, and a medulla (3–)5–8 cells across, inner cells ovoid and 80–150(–200) µmin diameter, with small-celled filaments lying between the larger cells in older branches. Rhodoplasts discoid, ribbon like in inner cells.

Reproduction.Early reproductive structures unknown. Carposporophytes with a basal fusion cell and gonimoblast cells all becoming ovoid carposporangia 45–100 µmin diameter. Basal nutritive tissue well developed, erect filaments disintegrating but cell walls of lower cells remaining. Cystocarps hemispherical, not or slightly basally constricted, 700–1200 µmin diameter, pericarp 100–200 µmand 8–12 cells thick, ostiolate. Spermatangia unknown. Tetrasporangia scattered in branches, transformed from outer medullary cells, 80–140 µmin diameter, tetrahedrally to cruciately divided.

Distribution. Champion Bay to Eucla, W. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 113–115 (1996)]