Laurencia tasmanica Hook.f. & Harv.

Scientific Description

Habit and structure. Thallus medium to dark brown-red, 10–25 cm high, robust, drying cartilaginous with one to several percurrent axes, pyramidal in outline, irregularly radially branched with clustered branched ramuli, branches terete; axes 2–3 mm in diameter, often denuded below, laterals 1–1.5 mm in diameter, decreasing to ultimate ramuli 0.5–1(–2) mm long and (0.5–)0.7–1 mm in diameter. Holdfast discoid, becoming stoloniferous; epilithic. Structure. Epidermal cells isodiametric and 10–15(–18) µm across near apices, enlarging to 15–30 µm broad and L/D 2–4(–5) in older parts, with secondary pit-connections and corps en cerise; cortical cells compact, without lenticular thickenings. Cells with discoid rhodoplasts.

Reproduction. Gametophytes dioecious. Procarps not observed. Carposporophytes with a basal fusion cell and much-branched gonimoblast with clavate terminal carposporangia 20–45 µm in diameter. Cystocarps sessile, broad based or slightly constricted, ovoid, 600–1200 µm in diameter; pericarp ostiolate, without a neck, 5–6 cells thick. Spermatangial receptacles ovoid to broadly clavate, 800–1200(–1500) µm across; spermatangia on trichoblasts. Tetrasporangial ramuli simple, in branched clusters, clavate, 1–3 mm long and 0.5–1 mm broad, cut off abaxially in parallel arrangement, 100–140 µm in diameter.

Distribution.Capel Beach, W. Aust., and American R. inlet, Kangaroo I., S. Aust., to San Remo, Vic., and around Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 468 (2003)]