Abstract: The floral organogenesis and development of Clematis fruticosa Turcz. were observed under scanning electron microscope (SEM). Four sepals are decussate in position and whorled phyllotaxis in arrangement. The primary four stamen primodia initiate spirally nearly in joint position of four sepals. Then, with the increasing of stamen primordium numbers, the phyllotaxis gradually change into slightly apparent spiral pattern. When initiation of stamen primordia have finished, carpel primordia initiate spirally along the initiation pattern of stamen primordia on the floral primordium apex. Our results support the viewpoint that the spiral phyllotaxis and the whorled phyllotaxis can coexist in a flower of primitive angiosperms. Furthermore, we also confirmed the view that sepal and bract are homologous.

Key words: Clematis, C.fruticosa Turcz., Ranunculaceae, floral phyllotaxis, floral organogenesis and development