A division of very variable, predominantly unicellular, flagellate *algae
. It contains both pigmented (autotrophic or facultatively heterotrophic) and unpigmented (obligately heterotrophic) genera. When pigments are present they are similar to those found in the Chlorophyta. A cell wall is absent, enabling certain of the unpigmented forms to ingest food by phagocytosis. Such forms are probably better classified as Protozoa even though they most likely evolved from photosynthetic forms. Food is stored as paramylum and fat.