Freshwater Algae Key

A1. Nonmotile algae without chloroplasts: Cyanobacteriophyta

B1. Vegetative cells usually solitary

B2. Vegetative cells united into colonies or agglomerations

C1. Cells arranged in a single layer to form flat colonies

C2. Colonies comprised of cubical, 4-cell subgroups

C3. Colonies spherical, oval, or amorphous (irregular) in shape

D1. Cells form tangled filaments enclosed in spherical or nearly spherical mucilage: Nostoc

D2. Cells appear mottled brown when viewed under the microscope

E1. Cells attached at ends of thick, radiating mucilage strands (rarely visible), forming single layer on outer perimeter of hollow colony: Woronichinia naegeliana

E2. Cells not attached to radiating mucilage strands; strands may be present but invisible under normal magnification

D3. Cells various colors but not mottled brown when viewed under the microscope

B3. Vegetative cells aligned end-to-end forming filaments or pseudofilaments

A2. Motile algae with chloroplasts and 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