Haraldiophyllum erosum (Harv.) A.Millar & Huisman

Scientific Description

Habit and structure. Thallus medium to dark red to red-brown, 5–13 cm high, subdichotomously to laterally complanately branched with branches 6–12 mm broad, reaching 25 mm broad at branchings; margins fringed with multicellular branched spinous processes 200–600 µm long, corticated basally, each with a single apical cell; midribs and veins absent. Holdfast discoid, with a short stipe; epilithic or epiphytic. Structure. Growth marginal but vague, with intercalary divisions, blades monostromatic and 25–60 µm thick apart from the base and reproductive areas, cells 25–35 µm across and L/D 1–2(–4).

Reproduction. Gametophytes dioecious. Procarps scattered over both surfaces, with primary cells cutting off 2 cells on each surface, becoming fertile on one side only with the distal cell developing as a cover cell group and the proximal cell acting as a supporting cell which produces a distal sterile cell and a 4-celled carpogonial branch, followed by a second sterile cell from the supporting cell. Carposporophytes with a basal fusion cell incorporating gametophytic cells on the cystocarp base, much branched gonimoblast and clavate to ovoid terminal carposporangia 20–35 µm in diameter. Cystocarps 0.6–1.5 mm in diameter, swollen to hemispherical, ostiolate; pericarp 60–200 µm and 6–7 cells thick, bearing branched processes in the ostiolar side. Spermatangial sori elongate, on both surfaces, with the primary cells producing cortical cells which divide anticlinally to 4 initials, each producing several spermatangia. Tetrasporangial sori ovate, scattered, 200–600 µm across and 90–130 µm thick, with 2 layers of tetrasporangia cut off from inner cortical cells which also produce the outer layer of cover cells; tetrasporangia subspherical, 35–60 µm in diameter.

Distribution.Houtman Abrolhos, W. Aust., to Western Port, Vic.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 126–128 (2003)]