Genus: Cell body long cylindroid; a slight constriction at center; cross section of the semicells spherical,
slightly swell at the center but without a folded structure as
Docidium; slightly tapered toward both ends, which are truncated and smooth or
surrounded by granules or various small structures; laterally straight or wavy, with spiny
projections in some species; 2-10 ribbon-like chloroplasts in each semicell;
with many pyrenoids; a vacuole containing active granules at both ends same as in
cell wall mostly dotted, but with spines or other patterns in some species
(Illustrations of The Japanese Fresh-water Algae, 1977).
Species [ var. gracile ]: Cell body cylindrical, 110-240 μm long, 6.5-15 μm wide, L/W=14-20; semicells not swelled at base, slightly tapered, with blunt and smooth ends; cell wall smooth or finely dotted; chloroplasts located along cenral axis, with about 6 laminae; pyrenoids arranged linearly, 3-7 in each semicells (Illustrations of The Japanese Fresh-water Algae, 1977).