Hymenena multipartita (Hook.f. & Harv.) Kylin

Scientific Description

Habit and structure. Thallus medium to dark red-brown, 5–10(–12) cm high, usually densely tufted, more-or-less complanately branched with alternate, marginal, flat branches 1–4(–10) mm apart, all branches 1–2(–3) mm broad, apices rounded, margins entire, smooth, older axes becoming denuded of laterals below and 0.5–2 mm broad. Holdfast rhizoidal, becoming fibrous; epilithic or epizoic. Structure. Growth marginal, without obvious apical cells, marginal cells 6–10 µm across. Blades mostly monostromatic and 50–90 µm thick, older parts 3 cells and 90–120 µm thick, cells angular to ovoid and 25–45 µm across, L/D 1–2. Central lower branches 200–500 µm and 7–14 cells thick, cells in anticlinal rows. Microscopical veins slight to prominent, slender, 1 cell broad, cells 20–30 µm in diameter and L/D 1.5–3.5(–5). Cells with discoid to elongate rhodoplasts.

Reproduction. Gametophytes dioecious. Procarps scattered on both sides of blades, with supporting cell bearing 2 sterile cells and a 4-celled carpogonial branch, surrounded by pericarp initials. Carposporophytes with a small basal fusion cell and much branched gonimoblast with clavate to ovoid carposporangia 25–40 µm in diameter. Cystocarps 700–1500 µm across, bulging on both sides especially the ostiolar side with a short, coarse neck; pericarp 200–400 µm and 6–8 cells thick, cells in anticlinal rows. Spermatangial sori covering ends of branches, cortical cells dividing anticlinally to form plates of initials each producing 2–4 elongate spermatangia. Tetrasporangial sori on branches, often near apices, 1(–3) per branch width, ovate, 200–500 µm across and 180–230 µm thick, with 2 layers of tetrasporangia cut off laterally from inner cortical cells which also produce the outer cover cells; tetrasporangia subspherical, 50–80 µm in diameter.

Distribution. Topgallant I., S. Aust., to Gabo I., Vic., and around Tas. New Zealand. Andaman and Nicobar I.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 139–141 (2003)]