Ptilophora prolifera (Harv.) J.Agardh

Scientific Description

Habit and structure. Thallus red-brown, 10–40 cm high, robust, irregularly branched below from the margins or surface of flat blades, usually largely covered with sponge between small surface proliferations, alternately pinnately branched and free of sponge for 1–5 cm below the apices; lower axis thickened, compressed to more-or-less terete at its base. Lower branches 5–10(–20) mm broad, tapering gradually to complanate pinnate terminal blades 1–4 cm long, with pinnae 2–5 mm long and 1–2(–3) mm broad, bare of both surface proliferations and sponge. Surface proliferations profuse except on young pinnate blades, usually emergent from the sponge cover, flat, irregularly to subpinnately branched, 1–2(–3) mm long, sometimes themselves proliferous. Holdfast branched, hapteroid, 1–6 cm across and 1–3 cm high; epilithic. Structure. Cortex 3–15 cells thick, with outer cortical cells in branched anticlinal rows (increasing in number in older branches) with the outermost cells 3–5 µm across in surface view and more-or-less in rows, then the inner 5–8 cells which become elongate and separated by abundant masses of rhizines; the innermost cortex comprises a zone 2–4 cells broad of distinctly larger, rounded and isodiametric cells; medulla of longitudinal filaments of moderately broad cells with thick walls, and few rhizines.

Reproduction. Cystocarps formed in surface proliferations which are usually slender and unbranched, with a single, swollen, bilocular cystocarp with a central placenta and an ostiole on each side; carposporangia terminal, elongate-ovoid to clavate, 15–20 µm in diameter. Spermatangia unknown. Tetrasporangia developed in surface proliferations, ovoid, 50–60 µm long and 20–30 µm in diameter, cruciately or decussately divided.

Distribution. Flat Rocks, S of Geraldton, to Albany, W. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 125–126 (1994)]