Abstract:Petiolar structure of 26 Osmanthus species was observed under light microscope. The results showed that there were rich variations among petiolar anatomical characters of Osmanthus. There are 3 types of cross section of petioles (U, V and Y types), the outmargin shapes of petioles are undulated, sinuolate or nearly smooth. Trichomes are present or not. In most species, there are 3 vascular bundles (one bigger and two smaller) in cross section of petioles. There are abundant variations on outline of vascular bundle among species. The vascular bundle types in cross section of petioles are amphicribral bundle, almost amphicribral bundle and collateral bundle. There is a pith cavity on center of vascular bundle in O. minor, O. matsumuranus, O. marginatus and O. americanus. Some species have sclerotic cell or stone cell. The anatomical characters of petioles could be used to circumscribe the species within Osmanthus as they are stable between different species.
