XVI International Botanical Congess

Verbascum was considered a link between Solanaceae and Scrophulariaceae because of its nearly actinomorphic, rotate corolla and five fertile stamens. Robertson (1891) inferred a tubular, bilabiate ancestry of Verbascum, an interpretation at odds with contemporary systematic hypotheses. Pennell (1935) agreed treating Verbascum as a more derived genus. Character polarity may be determined by molecular and ontogenetic data. Recent molecular data supports the Robertson/Pennell hypothesis. Thus the floral ontogeny of Verbascum was expected to show a heterochronic shift in development. Results of comparative ontogenetic studies of Verbascum, related genera, and selected outgroups support the reversal hypothesis, the corollar morphology, once interpreted as ancestral, is the result of a truncation in floral development.