Ganonema helminthaxis Huisman & Kraft

Scientific Description

Habit and structure. Thallus to 18 cm high, dull rose-red or brown, mucilaginous, uncalcified, irregularly radially branched to 2–4 orders, with or without a percurrent axis. Axes from 1.2 mm in diameter at the base to 0.5 mm in diameter near the apices. Medullary filament cells 20–1200 × 10–65 µm; rhizoids 5–8 µm in diameter. Assimilatory filaments 300–350 µm long, pseudodichotomous to trichotomously branched, with ellipsoidal to barrel-shaped cells 10–18 µm in diameter.

Reproduction. Dioecious. Spermatangia developing on short lateral or terminal branchlets of 3–6 fertile axial cells, the lowermost usually with 1 or 2 side branchlets of 3 or 4 secondary fertile axial cells, resulting in compound dendroid spermatangial clusters; each fertile axial cell bearing 3–8 spermatangial mother cells that, in turn, cut off 2–4 subspherical spermatangia 3–5 µm in diameter. Carpogonial branches 3–6-celled, straight, borne singly or in clusters of up to 3 from the distal end of inner cortical supporting cells or cells of rhizoidal filaments. Sterile filaments arising prior to fertilization, mostly from the supporting cell, occasionally from cells distal to and subtending it. Gonimoblast compact, obconical. Carposporangia obovoid to reniform, 28–31 × 12–18 µm; proliferation of carposporangia occurring a number of times within the old sporangial walls. Fusion cell absent. Sterile filaments richly branched, borne on the supporting cell and cells immediately below and above; at maturity with lateral and descending filaments surrounding the carpogonial branch and supporting cells, but not the carposporophyte. Cystocarps to 300 µm in diameter.

Distribution. Known only from the type collection (Point Clune, Rottnest I., W. Aust.) which includes one additional, spermatangial specimen.