Achene anatomy in Coreopsidinae (Heliantheae; Compositae) and its systematic implications

Abstract

Comparative anatomical study of achenes of the Bidens, Chrysanthellum, Coreopsis, Cosmos, Dahlia, Guizotia, Heterosperma, Isostigma and Thelesperma shows a strong similarity in the arrangement of the epidermis, hypodermis, phytomelanin layer, fibrous zone and the parenchymatous zone. Fibrous zone is continuous in all the taxa except in Guizotia where fibre bundles are formed. The cells of the seed coat do not show any type of thickening. Present study supports the placement of Guizotia in the Sub tribe Coreopsidinae as done by Stuessy (1977). However, we suggest placement of this genus in a separate group within Coreopsidinae.