The ultrustructural features of developing anthers of Michelia figo were studied using transmission electron microscope technique.The results are as following:(1)During pollen development,the vacuolization took place three times.The first time was the microspore mother cells (MMC) displayed evident vacuoles in the cytoplasm,which may relate with forming callose wall to separate the MMCs.Then the vacuoles appeared again in periplasm region of MMCs before its meiosis,which may relate with dissolving their cellulose wall.At the same time,many vacuoles appeared in the cytoplasm,increasing volume of cell and preparing for tetrad.The third time was the vacuolization which took place at late microspores.A big vacuole occupied most space of microspore,extruded its nucleus to periplasm,which created a polarity of microspore,preparing for asymmetric gametophytic division.(2)The sexine of exine of Michelia figo appeared first at the early microspore stage.The nexine of exine is synthesized at the late microspore.The intine of pollen grain was synthesized by vegetative cell of bicellular pollen.Finally,the degradating substance of tapetum cumulated on the surface of tectum of pollen grain to form the pollen coat.