XVI International Botanical Congess

The monotypic genus Cnicus L. is one of numerous small genera within Centaureinae subtribe, which are disputed and difficult from the taxonomic point of view. According to some investigators the majority of the genera from this group, including Cnicus, morphologically is closer to Centaurea L. representatives. As the features of achene microstructure are reliably diagnostic ones, we investigated achenial envelope microstructure of Cnicus benedictus L. for clarification of relationships between these genera. The results were compared with the published data for Centaurea representatives (Mouradian, 1999). The comparative analysis revealed similarity only in spermoderm structure ( well expressed testepiderm with radially elongated macrosclereids, well preserved parenchotesta, remains of endosperm, etc.). However representatives of these genera distinctly differ by pericarp structure. Thus C. benedictus has pericarp with 19-20 rather large, closely settled ribs with well-developed mechanical tissue, and pericarp domination. These features are not at all characteristic for Centaurea representatives and, in our opinion, it is a forcible argument for confirmation of the independence of the genus Cnicus.