Comparative Morpho-Anatomical Study of Cypselas in some Species of the Tribe Heliantheae (Asteraceae)

A comparative study of morphology and anatomy of mature cypselas in 14 species belonging to 10 genera, such as BIDENS, CHRYSANTHELLUM, COREOPSIS, COSMOS, ECHINACEA, GAILLARDIA, GLOSSOGYNE, HELIANTHUS, TITHONIA and XANTHIUM under the tribe Heliantheae (Asteraceae) was undertaken under light and scanning electron microscopes. Morphologically the form and structure of cypselas, carpopodia and pappus are diacritical for characterization of taxa. In all species pericarp is well differentiated into 2 zones. Cells of the epicarp are usually tangentially elongated, provided with yellow or brown substances. Mesocarp is mainly differentiated into 4 zones. Number and distribution of vascular traces, phytomelan layer and secretory cavities are taxonomically significant in certain taxa. An artificial bxonomic key using the detailed morphological, anatomical and SEM observations on the mature cypselas are provided.