Freshwater Algae Key

A1. NONMOTILE ALGAE WITHOUT CHLOROPLASTS: CYANOBACTERIA

B1. VEGETATIVE CELLS USUALLY SOLITARY

B2. VEGETATIVE CELLS UNITED INTO COLONIES

C1. CELLS ARRANGED IN A SINGLE LAYER FORMING FLAT COLONIES

C2. CELLS ARRANGED IN CUBICAL COLONIES

C3. CELLS ARRANGED IN SPHERICAL OR NEARLY SPHERICAL COLONIES

D1. CELLS ATTACHED TO RADIATING MUCILAGE STRANDS

E1. CELLS SPHERICAL, IN GROUPS OF 2 OR 4 AT END OF THIN, RADIATING MUCILAGE STRANDS: Snowella

E2. CELLS FORM AT END OF THICK, RADIATING MUCILAGE STRANDS; CELL DIVISION ALONG LONG AXIS FORMS HEART-SHAPED CELL PAIRS: Gomphosphaeria

E3. CELLS FORM AT END OF THICK, RADIATING MUCILAGE STRANDS THAT ARE RARELY VISIBLE; INDIVIDUAL CELLS SPHERICAL OR OVAL, NOT HEART-SHAPED; MOST COMMON SPECIES IS DARK MOTTLED BROWN: Woronichinia

D2. CELLS NOT ATTACHED TO RADIATING MUCILAGE STRANDS (STRANDS MAY BE PRESENT BUT INVISIBLE UNDER NORMAL MAGNIFICATION)

C4. CELLS ARRANGED INTO IRREGULAR, AMORPHOUS COLONIES

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

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)