Freshwater Algae Key

A1. Nonmotile algae without chloroplasts: Cyanobacteriophyta

A2. Motile algae with chloroplasts and flagella

B1. Motile single-cell algae

C1. Cells with one visible flagellum

C2. Cells with two equal length flagella

C3. Cells with two dissimilar flagella

D1. Cells with one forward and one trailing flagellum

D2. Cells with one transverse and one trailing flagellum (Dinoflagellates)

D3. Cells with two forward-directed or subapical flagella

E1. Cells tiny; lorica bowl-shaped, transparent, with spiralling ridges: Kephyrion and Pseudokephyrion

E2. Cells teardrop-shaped, golden brown, with very short, subapical flagella: Chlorochromonas danica

E3. Cells slipper-shaped, oval, teardrop-shaped; asymmetric; two nearly equal flagella inserted below apex (subapical): Cryptomonads

E4. Cells oval or spherical; cell wall contains knobby mucilage granules (no trichocysts): Vacuolaria

C4. Cells with more than two flagella

B2. Motile colonies with 4 or more cells

A3. Nonmotile algae with chloroplasts but without flagella

A4. Cells with paired, symmetric semi-cells: Desmids

A5. Cells enclosed in glassy, ornamental frustules: Diatoms