Mazoyerella arachnoidea (Harv.) Gordon-Mills & Womersley

Scientific Description

Habit and structure. Thallus dark red-brown, erect, 0.5–4(–5) cm high, forming slender, much branched tufts, subdichotomously branched every 1–3(–6) cells; prostrate filaments absent. Attachment by elongate multicellular rhizoids from lower axial cells. Epiphytic on Dasya villosa or probably epilithic. Structure. Apical and upper cells 4–16 µm in diameter and L/D 4–20, median cells (20–)25–50 µm in diameter and L/D 4–10, lower cells 100–250 µm in diameter and L/D 4–10. Cells multinucleate; rhodoplasts discoid to elongate, reticulate in larger cells.

Reproduction. Propagules on unicellular stalks on cells of erect filaments, single celled, elongate-ovoid, (40–)60–90 µm in diameter, multinucleate. Gametophytes dioecious. Procarps on the subapical cell of short 2-celled axes on a larger subhypogenous cell which develops a lateral branch, with 2 periaxial cells, one (the supporting cell) bearing a 4-celled carpogonial branch and a terminal sterile cell. Post-fertilization the auxiliary cell produces usually 3 gonimolobes 40–160 µm across of ovoid carposporangia 15–30 µm in diameter, and the sterile procarp cells (apical, sterile periaxial and supporting sterile cell) produces slender involucral filaments around the young carposporophyte. Spermatangial heads sessile on upper cells, slightly elongate, 35–35(–55) µm in diameter, with usually 4 axial cells producing initials radially and outer spermatangia. Polysporangia occur on upper cells, sessile, subspherical, 35–65 µm in diameter, with 8 or 16 spores.

Distribution.Troubridge Light to American R. inlet, Kangaroo I., S. Aust., and N Tas.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 302 (1998)]