Order & Family: Filamentous algae; cell division occurs near septum and adds "apical cap" (folded structure near the septum) ; cell body cylindrical, laterally straight or wavy or swell at one end of the cell body ("capitellate") in some species; chloroplasts reticulated with many pyrenoids; asexual reproduction by zoospore; sexual reproduction by fertilization by egg and sperm; monoecious or dioecious. Genus: linear filament without branching (Illustrations of The Japanese Fresh-water Algae, 1977).