An embryo containing only one zygote is called monosporic. About 75% of the plant kingdom is monosporic. In 1879, Strusberger first described the structure of the monosporic embryo of the plant Polygonum divaricatum. Monosporic embryos are of two types.
(i) Oenothera type: Oenothera is a 4-nucleate embryo sac. eg Oenothera lamarckiana.
(ii) Polygonum type: Polygonum is an 8-nucleate embryo sac. For example, Polygonum hydropiper.