Oogamy is the form of sexual reproduction which is a type of heterogamy. Also comes under the part of anisogamy. Oogamy is the fertilization process where the male gamete is received by the female and fusion occurs within the female gamete cell. The male gametes are motile and smaller, while the female gametes are larger and non-motile.
Such type of reproductive fertilization is observed in Gymnosperm, Bryophytes, and even Pteridophytes