Sesquiterpene lactones from Chrysolaena platensis.

A.L. Cabrera's treatment of Argentine Vernonias (Cabrera, 1944) included four members of his Section Lepidaploa, subsection Flexuosae, three of which were listed as occurring in Entre Rios Province (Cabrera, 1974). Two of these, V. cognata Less. and V. platensis (Spreng.) Less., were said to be closely related, di!ering from each other only in the number of #owers in the capitulum, diameter of the campanulate involucre and the thickness of the xylopodium. The two species were originally recognized by Jones (1979) as distinct members of his series Flexuosae (Cabr.) S.B. Jones but were later (Jones, 1980) without further discussion declared to be synonyms with the binomial V. platensis taking precedence over V. cognata. His description did not