Husseya rubra (Harv.) P.C.Silva

Scientific Description

Habit and structure. Thallus dark brown-red, 15–30 cm high, irregularly branched for 3–4 orders, branches terete, lower axes 1.5–2(–5) mm in diameter, grading to 0.5–1 mm in ultimate branchlets, axillary branchlets frequent; active branch apices depressed, when mature rounded, with prominent trichoblasts when young. Holdfast discoid, 4–5 mm across, becoming fibrous; epilithic. Structure. Apical cells hemispherical, 15–20 µm in diameter, with a short apical filament then broadening suddenly. Pericentral cells 5, equal in length to the axial cells, cortex broad and with 3–4 additional rings of larger cells separated by abundant development of rhizoids; the epidermis remains meristematic forming an extensive secondary cortex of small cells, sometimes with apparent growth rings. Epidermal cells 25–50 µm in diameter, L/D 1–1.5 when young, later elongate and L/D 2–6; on secondary thickened axes, outer cells isodiametric and about 100 µm in diameter. Cell wall thickenings present on the pericentral cells and sometimes cells of the next outer ring, increasing from strips to caps or rings, becoming massive and almost filling the cell. Trichoblasts 0.5–1 mm long. Cells with discoid to elongate rhodoplasts, chained in larger cells.

Reproduction. Procarps on the suprabasal cell of trichoblasts of short axillary branchlets. Carposporophytes with an erect fusion cell and short, branched gonimoblast with clavate terminal carposporangia 90–100 µm in diameter. Cystocarps with short stalks, ovoid with a small basal protrusion, 1–1.4 mm in diameter; pericarp ostiolate, lightly corticated, 150–200 µm thick. Spermatangial organs unknown. Tetrasporangial branches in axillary clusters, 2–5 mm long and 700–1200 µm in diameter, tetrasporangia cut off from pericentral cells, 80–170 µm in diameter.

Distribution.W. Aust., (Fremantle ? or Geographe Bay) to Cape Northumberland, S. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 420–422 (2003)]