This paper deals with the sexual reproduction of Catalpa fargesii f. duclouxii (Dode) Gilmour, including its differentiation of the flower bud, the microsporo-genesis, the formation of the pollen, the development of the male gametophyte and the formation of the ovule, the megasporogenesis, the formation of the female games tophyte, the fertilization and the development of the embryo and endosperm. The development of the embryo sac is of the Polygonum type and that of the embryo the Cruciferous type. Endosperm is cellular and eventually develops into haustorium cells in both mycropyle and chalazal. The matured seed consists of a seed coat and an orthoembryo with two thick cotyledons. The material examined were collected from 22-24 year-old trees in Nanjing from 1976 to 1978. A timetable for the development of the flower bud and seed is also given.