Carpelloid stamens in Papaveraceae J USS . and Brassicaceae B URNETT (Cruciferae J USS .) and their bearing on theories of gynoecium organization

A rather frequent floral abnormality is the homeotic replacement of stamens with free carpelloid organs. This phenomenon is caused by spontaneous or experimentally induced recessive mutations. The morphology of carpelloid stamens in Papaveraceae and Brassicaceae taxa is described on the basis of the author's observations as well as literature analysis. The number of carpels constituting the gynoecia of these families has been much debated. One widely accepted theory claims that carpel number equals the number of placental regions (at least two—bicarpellary theory). Other hypothesis consider pistils with two placental regions to be formed by four carpels (tetracarpellary theory) or even six carpels (hexacarpellary theory). Also an “acarpellate” condition with the paracarpous gynoecia being intercalary tubes topped by carpel rudiments was postulated. The structure of carpelloid stamens, however, strongly indicates that the classical bicarpellary theory can sufficiently explain the organization of papaveraceous and cruciferous gynoecia. The features that seemingly gave hints for double or triple numbers of carpels are already displayed by a (theoretical or real) combination of two gynoecial units which are represented by perfectly carpelloid stamens.