Unicellular, palmelloid or discoid green algae inhabiting in freshwater or on soil. Vegetative cell is uninucleate, possesses a parietal chloroplast with pyrenoid penetrayed by cytosolic tubes. There is no plasmodesmata. Asexual reproduction by means of quadriflagellate zoospores or autospores. In the quadriflagellate cells, four basal bodies are arranged in upper and lower pairs. The upper basal bodies are directly opposed, and the lower basal bodies are displaced clockwise. The flagellate cell is naked or covered by small scales. Sexual reproduction is unknown.