Alleynea bicornis Womersley
Mar.Benth.Fl.S.Australia 218-220 (2003)

Conservation Code: Not threatened
Naturalised Status: Native to Western Australia
Name Status: Current


IMCRA Regions: Eyre.

Scientific Description
John Huisman & Cheryl Parker, Thursday 8 September 2016

Habit and structure. Thallus dark brown-red, drying very dark, 10–30 cm high, with few to numerous erect, simple or branched, axes arising from an entangled, stoloniferous, base. Axes bear short determinate lateral branches radially and spirally, 1–3 mm apart, 2–4 mm long, branched 3–5 times subdichotomously and more-or-less complanately, with prominent bicornate ends. Attachment by short branches and compound multicellular rhizoids with multicellular haptera from stoloniferous branches; epilithic. Structure. Apical cells of axes and laterals hemispherical to dome-shaped, 15–20 µm in diameter, segmenting transversely or obliquely to form a lateral and the ultimate bicornate ends with pericentral cells cut off from the third to fifth axial cells. Pericentral cells 6, clear in transverse section, developing from close to apices a large-celled inner cortex and small-celled outer cortex. Axes 700–1200 µm in diameter below, tapering gradually to 300–600 µm in diameter near apices. Determinate laterals 250–350 µm in diameter near their base, tapering gradually to 80–100 µm in diameter at base of bicornate ends, then abruptly to the apical cells.Trichoblasts only seen on female plants, 300–600 µm long, coarse, basal cells 35–45 µm in diameter and L/D 1.5–2, upper cells 25–30 µm in diameter and L/D 2–3. Rhizoids cut off from pericentral cells. Cells uninucleate, larger cells multinucleate; rhodoplasts discoid, elongate and ribbon-like in larger cells.

Reproduction. Procarps on the suprabasal cell of trichoblasts, with a 4-celled carpogonial branch and 2–3 sterile cells. Carposporophyte with a small basal fusion cell and short, branched gonimoblast filaments with elongate-clavate terminal carposporangia 35–50 µm in diameter. Cystocarps ovoid, 400–600 µm in diameter; pericarp ostiolate, 2 cells thick, ecorticate, outer cells isodiametric and irregularly arranged. Spermatangial plants unknown. Tetrasporangial stichidia in irregularly branched clusters on the determinate laterals, ecorticate, usually curved, 0.5–1 mm long and 90–120 µm in diameter, with tetrahedrally divided tetrasporangia in gently spiral or almost straight rows, 50–100 µm in diameter, with 2 cover cells.

Distribution. Hopetoun, W. Aust., to Yorke Pen, and Stanley Beach, Kangaroo I., S. Aust.

Habitat. Apparently more common from the deep subtidal.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 219–220 (2003)]