A large number of single-celled flagellated algae form a motile free colony. There is no mucilage coating outside the colony. For example – Pyrobotrys.
5. Non-motile enveloped colony algae
Some non-motile unicellular algae form colonies by being enveloped in a gelatinous membrane. This is called a stationary covered colony. For example – Microcystis, Eucapsis etc.