Craspedocarpus venosus (Kütz.) Min-Thein & Womersley

Scientific Description

Habit and structure. Thallus erect, light to dark red, 5–15 cm high, complanately and generally subdichotomously to subtrichotomously branched, membranous, with flat branches 2–5 mm broad and 200–500 µm thick, usually slightly narrower basally than terminally, margins smooth, occasionally with small proliferations. Holdfast discoid; epilithic. Structure uniaxial, with the axial and periaxial filaments forming an alternately pinnate vein system (visible on staining), with rhizoidal filaments around the axial filaments forming the medulla, and a cortex 2–3 cells thick, inner cells ovoid and 50–100 µm in diameter, outer cells with well-developed rosettes of small cells 6–12 µm across which divide to completely cover the inner cells in older branches. Rhodoplasts discoid, few to numerous per cell.

Reproduction. Sexual thalli dioecious; procarpic. Carpogonial branches 3-celled, borne on inner cortical cells on the branch margins. Development as in C. blepharicarpus, resulting in a carposporophyte with several central cells, radiating gonimoblast filaments bearing chains of ovoid carposporangia 10–20 µm in diameter with some sterile filaments fusing with pericarp cells and also with cells of the inner nutritive tissue. Cystocarps marginal, protruding, 450–750 µm across, non-ostiolate. Spermatangia formed from rosette cells, with 3–4 initials each cutting off 2–3 ovoid spermatangia 2–3 µm in diameter. Tetrasporangia scattered in the outer cortex of young branches, ovoid 10–22 µm in diameter, zonately divided.

Distribution.Fremantle, W. Aust., to Westernport Bay, Vic., and Flinders I., Bass Strait.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIA: 423–425 (1994)]