Phormidium subfuscum Kütz. ex Gomont

Phycologia generalis: 195 (Kützing 1843). Tiffany & Britton, The Algae of Illinois 332, t. 90, f. 1044 (Tiffany & Britton 1952). Desikachary, Cyanophyta 273, t. 44, f. 22-23 (Desikachary 1959).

DESCRIPTION. — Trichome straight, blue-green or sometimes olive-green, not constricted at the cross-walls, generally cross-walls granulated, slightly narrow apically, sometimes sub-quadrate; end more or less briefly attenuated, capitate; end cells straight, acuteconical (Fig. 8L).

DIMENSION. — Trichome 5.4-11.0 µm broad and cells 2.1-3.9 µm long.

ENVIRONMENT & HABITAT. — Freshwater species; stagnant water; temperature 1°C.