The swimming cells may range in size from about 10 to nearly 100 micrometers in length. These plates are made of a complex polysaccharide, formerly believed to be cellulose. The insertion point of the two flagella is at the intersection of the girdle and sulcal groove. This intersection is defined as the ventralsurface of the cell. Plastids, when present, are golden-brown in color.
Cysts have thicker walls than swimming cells.
Some cysts, including the relatively short-lived hypnozygotes that participate in sexual reproduction, have similar plate tabulation to swimming cells. Other, presumably longer-lived cysts have plate tabulations that do not resemble those of swimming cells.