Feldmannia irregularis (Kütz.) Hamel

Scientific Description

Habit and structure. Thallus medium to dark brown, tufted, with numerous axes arising from a clumped base, mostly 0.2–1.5(–3) cm long, much branched in the lower half with long unbranched filaments surmounting the meristematic regions, usually epiphytic. Filaments 18–30(–40) µm in diameter below with cells L/B(1.5–)2–4, of fairly uniform diameter throughout and 20–35 µm in diameter above the upper meristem with cells becoming L/B3–6 and with few phaeoplasts. Growth from meristems at base of laterals and usually at intervals along main filaments, with occasional other diffuse divisions (especially where sporangia occur). Cells with numerous discoid phaeoplasts, each with a pyrenoid, and aggregated physodes.

Reproduction. Plurilocular sporangia usually sessile (rarely pedicellate), situated below upper meristems, single or in series of 2–3, often adaxial, of greatest diameter near their base and tapering markedly above, 60–100 µm long and 22–30(–45) µm in diameter. Unilocular sporangia ovoid, sessile.

Distribution. Widespread in temperate and warmer waters. In southern Australia, from Rottnest I., W. Aust., to Heron I., Qld.; probably more widespread.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 42 (1987)]