Myriogramme gunniana (Harv.) Kylin

Scientific Description

Habit and structure. Thallus dark red-brown, (5–)10–20(–30) cm high, foliose and usually irregularly divided or lacerate, branches mostly 1–3(–5) cm broad, terminally rounded, margins entire to very slightly dentate, surface often irregularly perforate (from grazing). Lower parts developing a central midrib, becoming stipe-like below by loss of lateral blades; microscopic veins absent. Holdfast becoming much divided and fibrous, 2–10 mm across; epilithic. Structure. Growth marginal with irregular intercalary submarginal divisions producing blades with irregularly arranged cells 15–35(–45) µm across and L/D 1–2 in surface view; occasional small marginal spines with small apical cells occur. Fronds monostromatic when young and 50–70 µm thick, soon tristromatic and 90–120 µm thick, becoming polystromatic in the midrib and where reproductive, with corticating cells equivalent and similar in size to the primary cells. Cells multinucleate, nuclei on anticlinal walls; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps scattered, with primary cells bearing a cover cell and a fertile pericentral cell with sterile cells and a 4-celled carpogonial branch. Carposporophytes with a basal fusion cell and much branched gonimoblast with short terminal chains of ovoid carposporangia 25–35 µm in diameter, maturing sequentially. Cystocarps scattered, 1–1.6 mm across, hemispherical; pericarp ostiolate, thick, with anticlinal filaments of isodiametric cells. Spermatangial sori ovate to elongate, 200–500 µm across and 80–100 µm thick with primary cells producing a layer of cortical initials with blocks of elongate spermatangia corresponding to the primary cells. Tetrasporangial sori scattered, ovate, 200–450 µm across and 150–250 µm thick, with tetrasporangia in 2 layers cut off from inner cortical cells and covered by smaller outer cortical cells; tetrasporangia subspherical, 45–65 µm in diameter.

Distribution.Probably from Whitford Beach, Perth, W. Aust., and Flinders I., S. Aust.; mainly from Port Elliot, S. Aust., to Walkerville, Vic., and around Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 108–110 (2003)]