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

C4. CELLS ANGULAR IN OUTLINE WITH THREE OR MORE SIDES

D1. CELLS 3-SIDED (TRIRADIATE) WITH LONG, STRAIGHT SPINES AT EACH ANGLE: Treubaria

D2. CELLS WITH 4-5 SIDES; FLATTENED (RECTANGULAR OR PENTAGONAL; NOT TETRAHEDRAL)

D3. CELLS 4 OR MORE SIDES; NOT FLATTENED; MOSTLY TETRAHEDRAL

E1. CELLS 4-SIDED (TETRAHEDRAL) WITH SHORT SPINES AT EACH ANGLE; GOLDEN BROWN; OFTEN EPIPHYTIC: Tetradinium

E2. CELLS 6-SIDED (HEXAGONAL), GOLDEN BROWN, WITH SMOOTH, THICK WALLS: Torviella cyst

E3. CELLS HIGHLY BRANCHED, NEARLY SPHERICAL, BRIGHT YELLOWISH GREEN: Pseudostaurastrum (in part)

E4. CELLS IRREGULARLY TETRHEDRAL AND STRONGLY TWISTED, WITH SHORT ANGULAR TEETH; BRIGHT YELLOWISH GREEN: Tetraplektron

E5. CELLS IRREGULARLY TETRHEDRAL WITH EVENLY PITTED SURFACE; BRIGHT YELLOWISH GREEN: Tetradriella

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)