Ptilocladia vestita (Harv.) E.M.Woll.

Scientific Description

Habit and structure. Thallus medium grey-red, 2–8(–10) cm high, spongiose, branches terete, irregularly to more or less alternately distichously branched, branches completely covered with whorl-branchlets except near active apices; axes and lower branches 1–2 mm in diameter, tapering to 150–300 µm near apices. Holdfast small, rhizoidal, 1–2 mm across; epiphytic on Posidonia, Amphibolis and various algae. Structure. Axes with short apical cells, enlarging to 20–25 µm in diameter and L/D 1–1.5 within a few cells, and increasing to 250–400 µm in diameter and L/D 2–2.5 in lower thallus, becoming corticate below with rhizoids from the basal cell of whorl-branchlets, with anticlinal filaments from the rhizoid cells in older parts. Whorl-branchlets in whorls of 4, 150–500 µm long, directed obliquely upwards, branched several times, basal cells 25–35 µm in diameter and L/D 2–2.5, tapering to short chains of terminal cells 7–10 µm in diameter and L/D 1.5–3; pyriform gland cells common on the whorl-branchlets; lateral branches arising from the basal cell of whorl-branchlets. Cells uninucleate; rhodoplasts elongate in smaller cells to ribbon like and anastomosing in larger cells.

Reproduction. Gametophytes dioecious. Procarps replacing whorl-branchlets near branch apices, with a supporting cell bearing a 4-celled carpogonial branch. Post-fertilization the auxiliary cell cuts off an upper cell which produces a rounded gonimolobe 200–500 µm across, with ovoid carposporangia 25–40 µm across, followed by later gonimolobes; the carposporophyte lies on elongate branches, surrounded by adjacent whorl-branchlets. Spermatangia are cut off from terminal cells of whorl-branchlets, ovoid, 3–4 µm in diameter. Tetrasporangia occur on lower cells of whorl-branchlets, sessile, subspherical, 45–65 µm in diameter, tetrahedrally divided.

Distribution. Exmouth, W. Aust., to Glenelg River mouth, Vic., and N Tas.

Habitat. P. vestitaappears to be usually epiphytic, especially on coralline algae often themselves on seagrasses or robust algae.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 60–61 (1998)]