Abstract: Taxonomists are divided over the infrageneric classification and species delimitation within the genus Cycas. The division is largely determined by whether a broad or narrow species concept is adopted, the latter approach being based on apparently minor morphological differences. It is well known that cytokinesis in the cells of pollen provides important evidence for plant taxonomy, particularly at the higher taxonomic level. Here we present the first broad comparison of the cytokinesis of male meiosis in five species of Cycas. A comparative analysis of microsporogenesis in Cycas was carried out using conventional microscopy, semi-thin sectioning, histochemistry, and fluorescence microscopy with a focus on the cytokinesis of meiosis in the pollen of dividing cells. Our observations confirmed that, contrary to previous reports, the cytokinesis in male meiosis of five species in Cycas is simultaneous at the end of second meiosis. The basic model of microsporogenesis and its systematic implications in Cycas is discussed based both on previous reports and our new results.

Key words: Cycas, cytokinesis, microsporogenesis, sectioning technique, systematic implication.