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:

100 μm 200 μm 300 μm; x 200 : 50 μm 100 μm 150 μm; x 400