Fig. 6

Tordylium brachytaenium. Morphogenesis of the umbel (A–D) and ray flowers (E–H). FUM fractionates umbellet meristems in a centripetal sequence. B Peripheral umbellets overtop central ones while fractionating FMs. Note the triangular shape of the umbellet meristems. C Ray flower meristems fractionate floral organs. Abaxial involucellar bracts are enlarged in comparison to adaxial ones. D Radial flower meristems fractionate floral organs. E First floral organs are initiated from the naked, pentagonal ray flower meristem. F Ray flower meristem before gynoecium initiation. G Peripheral umbellet with well-developed ray flowers not yet showing the enlarged petal lobes. H Ray flower bud showing enlarged abaxial petal lobes (Artedia-type zygomorphy). For colours and abbreviations, see Fig. 2. Scale bars = 100 µm