The fruits at different developmental stages of Calanthe tsoongiana were sectioned and observed through conventional paraffin section,semithin section and scanning electron microscope.The results showed that:(1)The ovule primordia began to differentiate from placenta 19 days after pollination.The ovule primordia was a layer of epidermal cells encircled a list of cells.The top cell differentiated into archesporial cell.Then archesporial cell differentiated directly into megaspore mother cell,45 days after pollination.(2)The mature ovule was anatropous,bi-integument and tenuinucellar.Development of embryo sac was polygonum type.Ovule development was not synchronized even in the same fruit.(3)The first zygote division was unequal,producing a basal cell and a terminal cell.The basal cell gave rise to the suspensor and it did not participate in the formation of embryo proper.The suspensor degenerated at the late stage of the embryo development.Terminal cell gave rise to embryo proper.Development of embryo was Caryophyllad type.(4)The shape of mature seed liked spindle.It consisted of globular embryo,endopleura and episperm.Endopleura and episperm developed from inner tegument and outer integument respectively.