Scytonematopsis Kiseleva (1930: 174)

Mcgregor, Glenn B., 2018, Freshwater Cyanobacteria of North-Eastern Australia: 3. Nostocales, Phytotaxa 359 (1), pp. 448-450 : 448-450

Scytonematopsis Kiseleva (1930: 174)

Type: S. woronichinii Kiseleva (1930: 174)

Filamentous, thallose; composed of solitary branched filaments which form clusters or mats on the substratum, or amongst other algae. Filaments free or densely coiled, creeping on the substratum, or joined to the substratum by middle parts and free ends of branches, sparsely or commonly falsely branched, usually with two, rarely one, branches. Branching initiates after trichome dissociation through the formation of necridic cells, rarely after loop-formation, not at heterocytes. Trichomes isopolar, ends of young trichomes and branches cylindrical with rounded terminal cells, later distinctly narrowed, sometimes with elongated, cylindrical, vacuolated apical and subapical cells; trichomes constricted or unconstricted at the cross walls. Sheaths firm, limited, hyaline or parallel lamellated, often yellowish-brown in colour in mature filaments. Vegetative cells shorter or longer than wide, pale or olive-green, rarely pinkish or bright blue-green, often elongated and vacuolated towards the ends, without aerotopes. Heterocytes intercalary, usually solitary, cylindrical or barrel-shaped, of different length. Cells divide crosswise to the trichome axis. Reproduction by hormogonia, which separate from the filament through the formation of necridic cells, liberated from the sheath, germinating at both ends.

A worldwide genus with 15 species currently taxonomically accepted; most are periphytic or metaphytic. Here one species is described from north-eastern Australia; one other species is known from elsewhere in Australia. Bibliography: Vaccarino & Johansen (2011), Komárek (2013).