Abstract:Megasporogenesis in Doritis pulcherrima collected from Hainan Province was observed undertransmission electron microscope. The megasporocyte is elliptical before the initiation of meiosis with its nucleus migrating toward the micropylar end and polarization being seen. The megasporocyte undergoes the first meiotic division, giving rise to two dyad cells. After meiosis Ⅰ, the chalazal dyad cell expands in size and differentiates into functional megaspore at the expense of the micropylar dyad cell. The functional megaspore undergoes the second meiotic division resulting in the formation of a binucleate embryo sac．The developmental pattem of the megasporogenesis in Doritis pulcherrima is ofbisporic Allium type．Some characters ofthe programmed cell death such as integrated plasma membrane， increasing amount of vacuoles， and hi dy compressed chromatin appears during the degeneration of the micropylar dyad cell， while the organelles distribute uniformity and the chromatin diffuses in the functional megasp qore．Some plasmodesmata occur on the chalazal cell wall of the functional megaspore but they disappear at the stage of binucleate embryo sac． Phagosomes wi th degenerated organelles are visible in functional megaspore at chalazal side.
