Genus: Trichome without mucous sheath; straight, long, consisting of numerous cells (Illustrations of The Japanese Fresh-water Algae, 1977). Species: Trichome blue-green in color, nearly straight or slightly curved, both ends slightly tapered and slightly curved, without constriction at cell-cell junction, 10-17 μm wide (cf. O. limosa, 15-20 μm); cell body short in length, 2-5 μm long (1/6-1/3 of its width); sometimes with granules along septum; terminal cells rounded with flattened apex (Illustrations of The Japanese Fresh-water Algae, 1977).

31 μm 63 μm 94 μm; x 640

Images of collecting locality: Saitama studium, Midori-ku, Saitama city, Saitama Pref., Japan, February 5, 2006 by Y. Tsukii