Abstract:

A natomic observation was made in the flower buds of Clematis glauca during flower bud differentiation with the paraffin-cut section. The results showed that flower bud differentiation of C. glauca could be divided into the undifferentiation phase，the initial differentiation phase，the primordial differentiation phase，the stamen differentiation phase，and the pistil differentiation phase，during the morphological differentiation period. The primordia of all floral organs initiated and developed centripetally. During the period of sexual cell differentiation and maturation，the male gametophytes matured faster than female gametophytes. The development of anther wall was the monocotyledonous type. Tetrasporangiate anther and glandular tapetum could be observed in C. glauca. Microsporocyte cytokinesis was successive，and microspores tetrads were mostly tetrahedral and occasionally symmetrical. In mature anther，the epidermis was degenerate completely or with a thin layer of remains left，and the endothecium was fibrous thickenings. Pollen grains of C. glauca were 2-celled. There was one chamber with few degraded ovules and a single normal one which was anatropous，unitegmic，tenuinucellate，and Polygonum type of embryo-sac with a linear tetrad of megaspores and dikaryocyte antipodal cells. The species might belong to evolutionary and transitional population relatively in the genus Clematis.

Key words: flower bud differentiation, sporogenesis, gametogenesis