The Cryptomonadaceae also are unicellular, and live free or in colonies.
The thallus may be unicellular or multicellular.
The spores of Monospora are by some regarded as unicellular propagula.
None of the existing Red Seaweeds (Rhodophyceae) has a unicellular body.
It is true that in the unicellular plants all the vital activities are performed by a single cell, but in the multicellular plants there is a more or less highly developed differentiation of physiological activity giving rise to different tissues or groups of cells, each with a special function.