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 cells 66-200 μm long, 40-50 μm diam.; 1 chloroplast making 3-5 turns in each cell; conjugation scalariform, tubes formed from both side; zygospores broad or short ellipsoidal, 50-83 μm long, 40-50 μm wide, internal layer yellowish, spre-surface smooth

50 μm 100 μm 150 μm; x 400