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Background  In the classical doctrines,  Magnolia  was frequently considered the archetype among flowering plants, and its conduplicate carpel with marginal placentation was assumed to be derived from a leaf-like organ bearing ovules along its margins. Although the robustness of this concept has been seriously questioned by advances in botanical research, especially the emergence of  Magnolia  deeper in the angiosperm tree of life in molecular systematics, it remains the most-taught interpretation for the origin of carpels.    Results  To test the validity of this classical doctrine, we performed comparative anatomical analyses of the vascular bundles in the flowers of  Magnolia  using fine (8-μm) paraffin -sections. We document the presence of two independent vascular systems in the carpels: the collateral bundles of the dorsal and ventral veins arising from the stelar bundle, and the amphicribral ovular bundles arising from the cortical bundles. This observation in conjunction with data from other fields concurrently suggests that the ovary wall is equivalent to a foliar organ whereas the placenta represents an ovule-bearing shoot.    Conclusions  Our observation on the former model plant,  Magnolia , nullifies the classical doctrine of carpel evolution and supports the Unifying Theory. This conclusion prompts a reconsideration of the concept of angiosperm flower evolution.    Electronic supplementary material  The online version of this article (doi:10.1186/1999-3110-55-28) contains supplementary material, which is available to authorized users.

From leaf and branch into a flower: Magnolia tells the story