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Lasiothalia hirsuta Harv.

Trans.Roy.Irish Acad. 558 (1855)
Conservation Code
Not threatened
Naturalised Status
Native to Western Australia
Name Status

Scientific Description

Habit and structure. Thallus erect, red brown to grey brown, 10–20(–30) cm high, with irregularly branched, densely corticated axes, with an inner entwined rhizoidal layer and an outer pilose layer of unbranched filaments, ecorticate near the apices only. Holdfast rhizoidal, 3–8(–12) mm across, epilithic. Structure. Axial cells 100–250 µm in diameter and L/D 2–6 in mid thallus, to L/D 10–20 in lower parts, each cell bearing first a single and later an opposite (usually less well developed) lateral branchlet, each furcate several times and usually with a smaller basal cell; these branchlets soon obscured by the cortication. Rhizoidal filaments from the lower cells of branchlets form a dense cortical layer, often anastomosing, with each cell producing a determinate, simple, outwardly projecting filament which is curved upwardly, 8–20 µm in diameter, 150–700 µm long, cells L/D 1–2.5. Denuded plants, without growing tips and pilose filaments, are frequent; gland cells absent. Cells uninucleate; rhodoplasts discoid in smaller cells, ribbon like in larger axial cells.

Reproduction. Gametophytes dioecious. Procarps borne near the tips of pilose cortical filaments, single or on several successive cells with the uppermost procarp usually on the third cell from the apex; the supporting cell, which bears the 4-celled carpogonial branch, is the basal cell of a short lateral branch 3–4 cells long, borne on the axial cell of the pilose filament. Post-fertilization the supporting cell cuts off an auxiliary cell and the carposporophyte consists of successive rounded groups 120–180 µm across of ovoid carposporangia 12–25 µm in diameter; the supporting cell, axial cell of the pilose branchlet and part of the lower axial cell fuse, but no involucral branchlets are produced. Spermatangial heads are borne on pilose cortical filaments and on lateral branchlets, each ovoid and 20–40 µm in diameter, L/D 1.5–2.5, with a basal pedicel and axis of 3–6 cells bearing whorls with terminal spermatangia 1–2 µm in diameter. Tetrasporangia are borne on short lateral branches of the pilose filaments, sessile or usually on 1–2-celled pedicels, subspherical, 35–55 µm in diameter, tetrahedrally divided.

Distribution.Cape Riche, W. Aust., to Robe, S. Aust., and the N coast of Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 38–39 (1998)]