Polysiphonia is a red alga. In it, sexual reproduction is of oogamous type. The male sex organ, spermatangium produces non-flagellate male gametes.
In brown algae, sexual reproduction varies from isogamy, anisogamy and oogamy. In isogamy and anisogamy, both the gametes are motile while in oogamy only male gametes are motile. These motile gametes have two unequal laterally attached flagella.
Chlorella is a unicellular organism. It is green algae belonging to class Chlorophyta. In Marchantia, gemma cups are found on its dorsal surface. It contains gemma which helps in vegetative propagation.