Freshwater Algae Key

A1. NONMOTILE ALGAE WITHOUT CHLOROPLASTS: CYANOBACTERIA

B1. VEGETATIVE CELLS USUALLY SOLITARY

B2. VEGETATIVE CELLS UNITED INTO COLONIES

B3. VEGETATIVE CELLS ALIGNED END-TO-END FORMING FILAMENTS OR PSEUDOFILAMENTS

C1. CELLS ARE JOINED END-TO-END TO FORM TRICHOMES; TRICHOMES CONTAIN HETEROCYSTS

D1. TRICHOMES UNBRANCHED, LACKING BOTH FALSE AND TRUE BRANCHING; MAY BE STRAIGHT, CURVED, OR TWISTED

D2. TRICHOMES WITH FALSE BRANCHING

D3. TRICHOMES FORM TRUE BRANCHES; TRICHOMES MAY BE UNISERIATE (ONE CELL WIDE) OR MULTISERIATE (TWO OR MORE CELLS WIDE)

E1. CELLS SPHERICAL, OVAL, OR BARREL-SHAPED; MAIN TRICHOME USUALLY MULTISERIATE (MORE THAN ONE WELL WIDE): Stigonema (in part)

E2. CELLS CYLINDRICAL OR BARREL-SHAPED; TRICHOMES MOSTLY MONOSERIATE (ONE CELL WIDE), SURROUNDED BY CLEAR, DIFFUSE MUCILAGE: Hapalosiphon and Fischerella

E3. CELLS OVAL OR SHORT, ROUNDED RECTANGULAR (L<W); TRICHOMES MOSTLY MONOSERIATE (ONE CELL WIDE), SURROUNDED BY FIRM, YELLOWISH MUCILAGE: Stigonema (in part)

C2. CELLS ARE JOINED END-TO-END TO FORM TRICHOMES; TRICHOMES DO NOT CONTAIN HETEROCYSTS

C3. CELLS FORM PSEUDOFILAMENTS WHERE INDIVIDUAL CELLS ARE ALIGNED END-TO-END BUT NOT JOINED ACROSS THE END WALL

A2. NONMOTILE ALGAE WITH CHLOROPLASTS

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)