Wrangelia plumosa Harv.

Scientific Description

Habit and structure. Thallus purplish-red to yellow-red, (2–)5–10(–25) cm high, alternately pinnately branched for 3–4 orders, outline broadly pyramidal. Holdfast discoid, 2–8 mm across, rhizoidal; epilithic. Structure. Apical cells dividing slightly obliquely and enlarging gradually to 400–500 µm in diameter and 1.5–2.5 mm long near the base. Each axial cell with 5 whorl-branchlets, developed from periaxial cells cut off usually in alternating order. Mature whorl-branchlets 1–2 mm long, overlapping only near branch apices, subdichotomously branched 5–8 times with ultimate branches 2–4(–6) cells long, median cells (20–)40–70 µm in diameter and L/D (3.5–)5–8, terminal cells 12–20 µm in diameter and L/D 2–6. Indeterminate lateral branches arising from basal cells of first-formed whorl-branchlets. Cortication by descending rhizoids from the basal cells of whorl-branchlets, forming a cortex up to 1 mm thick. Cells uninucleate; rhodoplasts discoid, in chains and reticulate in larger cells.

Reproduction. Gametophytes dioecious. Procarps formed successively on up to 7 axial cells, supporting cell without a terminal sterile cell. Post fertilization development as in W. abietina, with usually only one carposporophyte per fertile axis, carposporophyte with intermixed sterile whorl-branchlets, the whole subspherical and 450–900(–1200) µm across. Spermatangia terminal on radiating filaments of subspherical pedicellate heads reduced to fewer and shorter involucral cells. Tetrasporangia are terminal on short filaments arising from lower cells of modified whorl-branchlets, each sporangium surrounded by 2–5 curved involucral branches; tetrasporangia 50–80(–100) µm in diameter, tetrahedrally divided.

Distribution. Shark Bay, W. Aust., to Coffs Harbour, N.S.W. and around Tas.

Habitat. W. plumosa is common in lower eulittoral or uppermost sublittoral habitats.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 27–28 (1998)]