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: branching filaments; no spiny hairs; with rhizoids (Illustrations of The Japanese Fresh-water Algae, 1977).