Phitymophora amansioides (Sond.) Womersley

Scientific Description

Habit and structure. Thallus medium to dark red, 5–10(–15) cm high, much branched from the midrib with linear, corticated, secondary and tertiary branches 1–8 cm long and 2–3(–5) mm broad, bearing central rows of numerous small, ovate, bladelets 1–2 mm long, with short terete stipes, and which bear the reproductive organs. Holdfast discoid, 1–3 mm across; usually epiphytic on stems of Amphibolis. Structure. Apical cells obconical, segmenting to give an axial row with each cell cutting off first 2 lateral pericentral cells then 2 transverse ones, the lateral cells forming second-order rows with the inner 2–4 cells of the upper rows forming third-order rows and some (but not all) of the outer second-order rows also forming third-order rows; all rows reaching the blade margins. Cortication commencing early and becoming complete over the whole blade, 3–4 cells thick over the wings (thicker with elongate cells over the midrib), with large and small cells and rhizoids intermixed ; inner (primary) cells becoming 80–100 µm across, more or less isodiametric, with the outer cortical cells angular and mostly 10–15 µm across. Cells uni- to multinucleate; rhodoplasts discoid.

Reproduction. All reproductive organs borne on the small ovate blades on the midrib. Gametophytes dioecious. Procarps borne in series on transverse pericentral (supporting) cells, with 2 (?) sterile groups and a 4-celled carpogonial branch. Carposporophyte much branched with a basal fusion cell and short terminal chains of ovoid carposporangia 15–25 µm in diameter. Cystocarps hemispherical, 0.7–1 mm across, with corticated pericarp 4–5 cells thick and a small ostiole. Spermatangial sori covering both sides of the small bladelets, sometimes spreading over the midrib, with spermatangia cut off from outer cortical cells. Tetrasporangial sori on both sides of the bladelets, usually adjacent to the sterile midribs and sterile outer half or more of the bladelets, tetrasporangia cut off from inner cortical cells in 2 irregular layers of differing ages, with smaller outer cortical cells; tetrasporangia subspherical, 30–45 µm in diameter, tetrahedrally to decussately divided.

Distribution.Waterloo Bay, S. Aust. to Walkerville, Vic., and to Twofold Bay, N.S.W., S Indian Ocean.

Habitat. P. amansioides is a common and distinctive species, usually on stems of Amphibolis.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 63–65 (2003)]