Leaf anatomy applied to the taxonomy of Amazonian species of Oenocarpus Mart. (Arecaceae)

(Leaf anatomy applied to the taxonomy of Amazonian species of Oenocarpus Mart. (Arecaceae)). Our aim was to study the leaf anatomy of Oenocarpus bacaba Mart., O. distichus Mart., O. mapora H. Karst, and O. minor Mart. in order to verify if there are qualitative anatomical features useful in taxonomy. Common features of the four species' leaflets are amphistomatic lamina; heteromorphic epidermal tissue; smooth cuticle; epicuticular wax in the form of hooked filaments and rectangular plates; tetracytic stomata; non-glandular. two-filamented trichomes; dorsiventral mesophyll with brachysclereids, mucilage secretory structures, type III secondary, with three metaxylem vessels, and tertiary vascular bundles. However, cyclocytic stomata; number of expansion tissue layers; shape of midrib and edge were peculiar to some taxa. The middle and central regions of the leaf axis differ among Oenocarpus Mart. species in cell shape and organization of the parenchyma tissue. An anatomical key is given for the species of Oenocarpus Mart., showing that there are significant qualitative structural differences among these species.