The Cryptomonadaceae also are unicellular, and live free or in colonies.
The thallus may be unicellular or multicellular.
Many forms, even when multicellular, have all their cells identical in structure and function, and are often spoken of as physiologically unicellular.
These are unicellular algae characterized by the silicified cell made by two halves.
The green plants (including both multicellular and unicellular green algae) and the red algae.