A1. Nonmotile algae without chloroplasts: Cyanobacteriophyta

A2. Motile algae with chloroplasts and flagella

D1. Colonies parasitic on tree pollen; cells pyramidal, with short apical spine, often lacking chlorophyll; cells joined by short extensions to form open, spherical colony: Ducellieria

E1. Lorica attached to plant host by very short, thick stipe, or appearing to be sessile; lorica with narrow opening: Derepyxis

E2. Lorica attached by long stipe: Stylochrysalis

E3. Urn-shaped lorica attached to mucilage surrounding host plant by stipe that is slightly longer than the lorica: Epipyxis aureus

D3. Protoplasts (living portion of cell) not enclosed in rigid lorica; cell wall may be rigid or flexible

C2. Cells, colonies, filaments or pseudofilaments attached or associated with or attached to aquatic animals (epizoic)

C3. Chlorella-like cells living inside zooplankton and other aquatic animals (endozoic): Zoochlorella group

B2. Nonmotile solitary and colonial algae; cells not (or usually not) epiphytic, epizoic, or endozoic

B3. Nonmotile algae that form filaments or pseudofilaments

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

A5. Cells enclosed in glassy, ornamental frustules: Diatoms