Freshwater Algae Key

A1. NONMOTILE ALGAE WITHOUT CHLOROPLASTS: CYANOBACTERIA

A2. NONMOTILE ALGAE WITH CHLOROPLASTS

B1. CELLS USUALLY SOLITARY

C1. CELLS ENCLOSED IN RIGID LORICA, TEST, OR THICK WALLED CYST

C2. CELLS SPHERICAL, OVAL, ELLIPTICAL, OR LEMON-SHAPED IN OUTLINE

C3. CELLS CLUB-SHAPED, CRESCENT-SHAPED, ELLIPTICAL, OR FUSIFORM IN OUTLINE

D1. CELLS CLUB-SHAPED IN OUTLINE

D2. CELLS BROADLY OR NARROWLY CRESCENT-SHAPED; GENTLY OR STRONGLY CURVED

D3. CELLS BROADLY OR NARROWLY FUSIFORM IN OUTLINE

D4. CELLS ELLIPTICAL OR CYLINDRICAL IN OUTLINE

E1. CELLS CYLINDRICAL, SOLITARY, STRAIGHT OR SLIGHTLY CURVED; LONG APICAL AND POSTERIOR SPINES: Centritractus

E2. CELLS CYLINDRICAL (OR CLUB-SHAPED); SOLITARY AND COILED OR IN TREE-LIKE COLONIES WITH CELLS FORMING AT END OF ELONGATED PARENT CELL: Ophiocytium

E3. CELLS BROADLY FUSIFORM OR CYLINDRICAL; RIBBON-LIKE SPIRALLING CHLOROPLAST(S) OR DENSE CHLOROPLAST WITH REDDISH END CAPS: Spirotaenia and Tortitaenia

E4. CELLS FUSIFORM OR CYLINDRICAL; SOLITARY OR IN IRREGULARLY SPHERICAL COLONIES; CELLS ALIGNED ALONG LONG AXIS FORMING BUNDLES; COLONIES SURROUNDED BY DIFFUSE MUCILAGE: Quadrigula

C4. CELLS ANGULAR IN OUTLINE WITH THREE OR MORE SIDES

B2. NONMOTILE COLONIES WITH TWO OR MORE CELLS

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)