Genus: Colonies of 4 (or 2, 8, 16) cells attached side by side, arranged linearly or zigzag; cell body elliptical or spindle or crescent in shape; terminal cells with spiny projections in many species; cell wall usually smooth, but in some species granulated or dented or ridged (Illustrations of The Japanese Fresh-water Algae, 1977). Species:

31 μm 63 μm 94 μm; x 640

Scenedesmus obtusus Meyen var. obtusus: Colonies within a gelatinous envelope, flat or slightly curved; 4 cells arraned in alternate series, sometimes in cruciate series, 8 cells arranged in alternate or various double series; cell body ovate or elliptical, up to 16.5 μm long, up to 9.5 μm wide, termini of each cell may have a single nodular thickening; cell wall smooth; a single chloroplast with one pyrenoid (Photomicrographs of the Freshwater Algae, vol. 4, 1985).