Stictyosiphon soriferus (Reinke) Rosenv.

Scientific Description

Habit and structure. Thallus light to medium brown, 10–15(–30) cm high, slender, terete, much branched irregularly alternately (frequently opposite when young), tapering gradually from base to apices; attachment by a small, discoid, rhizoidal holdfast, epilithic. Structure below the apical trichothallic filament uniseriate for 10–50 cells, (l 0–)15–20 µmin diameter with cells L/B0.3–0.7, becoming polystichous below and 30–40 µmin diameter in upper branches, 200–400 µmin diameter in lower branches, branches solid apart from oldest parts, with a monostromatic, small-celled, cortex of phaeoplastic cells, more or less isodiametric and angular, 15–30(–35) µmacross in surface view and L/B1–2, and a large-celled medulla of 3–5 rounded, isodiametric cells with smaller cells below the cortex in older branches; cells in tiers in young branches, less so in older parts with the cortical cells subdividing and 4–8 within the old cell wall; phaeoplasts numerous per cell, each with a pyrenoid, and with prominent physodes. Phaeophycean hairs numerous, usually solitary, scattered, 5–8(–10) µmin diameter. Microthallus filamentous, pulvinate (unknown for Australian plants); macrothallus reproduced directly.

Reproduction. Plurilocular sporangia in scattered patches, formed by subdivision of one or a small group of cortical cells and slightly raised above the cortex, 20–40 µmacross in surface view with 4–6 locules in face view, each 2–4 locules high, each locule 2–3 µmacross.

Distribution. In southern Australia, from Albany, W. Aust., to Port Phillip, Vic., in harbours.

[After Womersley, Mar. Benthic Fl. Southern Australia II: 314 (1987)]