Genus: Filament without branching; cell body cylindrical; one or several chloroplasts band-shaped, spirally arranged within the cell, pyrenoids present; septum with or without folded structure (Guide book to the "Photomicrographs of the Freshwater Algae", 1998). About 300 species (Illustrations of The Japanese Fresh-water Algae, 1977). Species:

31 μm 63 μm 94 μm; x 640

Images of collecting locality: a pond near the entrance of climbing route to Omine mountain, Minakami town (formerly Tsukiyono town), Gunma Pref., Japan, May 25, 2006 by Y. Tsukii