Ptilocladia pulchra Sond.

Scientific Description

Habit and structure. Thallus medium to dark red-brown, 5–15(–30) cm high, spongiose, branches terete, alternately subdistichous to irregular, usually pyramidal in form with long axes or lateral branches and progressively shorter second and third order laterals towards their apices; branches completely covered with whorl-branchlets; axes and lower branches 1–2 mm in diameter, decreasing gradually to 0.6–1 mm in diameter near branch apices. Holdfast rhizoidal, 1–3 mm across; epilithic. Structure. Axes with short apical cells 12–15 µm in diameter and L/D 0.5–1, increasing to 350–500 µm in diameter and L/D 1–2 in lower thallus, becoming densely corticate with entwined rhizoids from the basal cells of whorl-branchlets, with cells of the inner layer of rhizoids enlarging and the outer layer producing scattered, anticlinal, short filaments; lateral branches arising from the basal cell of whorl-branchlets. Whorl-branchlets in whorls of 4 per axial cell, 300–450 µm long, di- or trichotomous 5–7 times, basal cells 50–80 µm in diameter and L/D 1–1.5, tapering to terminal cells 10–15 µm in diameter and L/D 1–1.5, terminating in a short row of 2–3 ovoid cells, often with a hair; gland cells absent, mature axial cells often containing crystal-like inclusions. Cells uninucleate; rhodoplasts elongate, ribbon like in larger cells.

Reproduction. Gametophytes dioecious. Procarps situated on the basal cell of shorter whorl-branchlets several cells below the apices of short determinate branches, with a supporting cell bearing a curved, 4-celled, carpogonial branch. Post-fertilization fusion with the auxiliary cell occurs via a connecting cell and the auxiliary cell divides to a lower foot cell and an upper cell which produces 2–3 successive, lateral, rounded gonimolobes 250–450 µm across of carposporangia 25–40 µm across. The carposporophyte is on a short lateral branch surrounded by adjacent whorl-branchlets. Spermatangia are cut off from terminal cells of whorl-branchlets, ovoid, 2–4 µm in diameter. Tetrasporangia occur on mid-cells of whorl-branchlets, sessile, subspherical to ovoid, 50–75 µm in diameter, tetrahedrally to subcruciately divided.

Distribution.Near Fremantle, W. Aust., to Queenscliff, Vic., and N Tas.

Habitat. P. pulchra is often common in pools on rough-water coasts, extending to 13 m deep.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 57–60 (1998)]