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: Vegetative cellls 68-190 μm long, 50-80 μm diam., 5-8 chloroplasts straight or slightly curved; conjugation scalariform, tubes formed from both gametangial cells; zygospores compressed spherical, 70-75 μm diam., medial spore wall thick, 3-5 μm in thickness, brown, smooth when matured (Photomicrographs of the Fresh-water Algae, 1985).