Abstract: Using traditional paraffin wax section, fluorescence microscopy, cytochemistry and TEM techniques, the megasporogenesis and development of female gametophyte of Cynanchum otophyllum Schneid were observed in detail. The results showed C.otophyllum was marginal placenta; the ovules are anatropous, tenuinucellate and unitegmic; some endoplasm, starch grains and mitochondria exist in nucellus; the archesporial cell is hypodermal in origin and directly gives rise to the megaspore mother cell; the chalazal megaspore functions to give rise to an 8-nucleate embryo sac, the embryo sac is of the ‘Polygonum type’ and shows the presence of starch grains in the mature condition; fertilization is porogamous; the endosperm passes through an early free nuclear stage before becoming cellular about the stage of 16-32 nucleate; as usual, the endosperm nucleus divides earlier than the zygote; the mature endosperm cells are uninucleate and irregular in outline; the presence of endosperm haustoria was not observed; development of embryo passes through the stages of proembryo, embryo of globular stage and embryo of heart stage and is of the ‘Soland type’; Seeds are comose and the coma develops from the epidermal cells of the integumentary tissue; a lot of fat pellets exist in mature endosperm.

Key words: Cynanchum otophyllum Schneid, megasporogenesis, female gametophyte