Freshwater Algae Key

A1. NONMOTILE ALGAE WITHOUT CHLOROPLASTS: CYANOBACTERIA

A2. NONMOTILE ALGAE WITH CHLOROPLASTS

B1. CELLS USUALLY SOLITARY

B2. NONMOTILE COLONIES WITH TWO OR MORE CELLS

C1. CELLS FLATTENED, FORMING RIBBON-LIKE CHAINS, SHORT CYLINDERS, OR PLATE-LIKE GROUPS OF CELLS

D1. COLONIES JOINED ON LONG AXIS TO FORM FLAT RIBBON-LIKE COLONIES (SINGLE ROW) OR PLATE-LIKE COLONIES (DOUBLE ROWS)

D2. CELLS FORM DISTINCT GROUPS OF 4; COLONIES MOSTLY RECTANGULAR IN OUTLINE

E1. RECTANGULAR 4-CELL COLONIES WITH FLATTENED, WEDGE-SHAPED CELLS; SOME TAXA MAY ALSO HAVE 8-CELL SPHERICAL COLONIES WITH WEDGE-SHAPED CELLS

E2. COLONIES COMPRISED OF 4-CELL GROUPS; CELLS BRIGHT GREEN, OVAL, ELLIPTICAL, OR BROADLY WEDGE-SHAPED: Crucigenia, Crucigeniella, and Willea

E3. COLONIES COMPRISED OF 4-CELL GROUPS, FORMING IRREGULAR, SOMEWHAT RECTANGULAR CLUMPS; CELLS GOLDEN BROWN; USUALLY EPIPHYTIC: Plaeoplaca

D3. COLONIES CIRCULAR OR OVAL IN OUTLINE; CELLS NOT IN DISTINCT GROUPS OF 4X

C2. COLONIES SPHERICAL OR OVAL

C3. COLONIES VARIOUS SHAPES OTHER THAN FLATTENED AND SPHERICAL/OVAL

B3. FILAMENTOUS ALGAE (INCLUDING PSEUDOFILAMENTS)

B4. CELLS ATTACHED TO ZOOPLANKTON (EPIZOIC), LIVING INSIDE ZOOPLANKTON OR OTHER AQUATIC ANIMALS (ENDOZOIC), OR ATTACHED TO AQUATIC PLANTS (EPIPHYTIC)

A3. MOTILE ALGAE WITH CHLOROPLASTS AND FLAGELLA

A4. CELLS DIVIDED INTO MIRROR-IMAGE SEMI-CELLS: Desmids (see key at cedar.wwu.edu/cedarbooks/14/ )

A5. CELLS ENCLOSED IN GLASSY, ORNAMENTAL FRUSTULES: Diatoms (see key at diatoms.org)