Freshwater Algae Key

A1. Nonmotile algae without chloroplasts: Cyanobacteriophyta

A2. Motile algae with chloroplasts and flagella

B1. Motile single-cell algae

B2. Motile colonies with 4 or more cells

C1. Cells with two equal flagella in colonies with 4 or more cells

D1. Flat colonies with 4-16 spherical or oval cells: Gonium and Tetrabaena

D2. Spherical, oval, or elliptical colonies (not flat)

E1. Spherical colonies with 16-32 compressed, wedge-shaped cells: Pandorina

E2. Spherical colonies with 16-32 spherical or oval cells (not wedge-shaped): Eudorina

E3. Large colonies with more than 250 tiny cells: Volvox

E4. Large colonies with 32-128 cells; large and small cells on opposite hemispheres: Pleodorina

C2. Cells with two dissimilar flagella

A3. Nonmotile algae with chloroplasts but without flagella

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

A5. Cells enclosed in glassy, ornamental frustules: Diatoms