Fig. 2

Echinophora trichophylla. Morphogenesis of the umbel (A–F, I) and ray flowers (G, H). To better visualize differences in promotion, a single umbellet from selected ontogenetic stages is marked with green shading with its ray flowers coloured red. A Large, naked FUM. B FUM fractionates peripheral umbellet meristems as common primordia with involucral bracts. C Central umbellet meristems follow. D Peripheral umbellets overtop central ones and fractionate common ray flower/involucel primordia. Note the persistent naked centre of the FUM. E Radial flower meristems follow. Note the bulging of the naked centre of the FUM. F Radial flower meristems fractionate floral organs. Ray flower meristems become zygomorphic G First floral organs are initiated from ray flower meristem in group-like patterns. H Ray flower meristem before gynoecium initiation. Note enlarged abaxial sepals (sp 1, 3) and zygomorphic symmetry of the meristem. I Late-stage of umbel development in longitudinal section. The naked centre of the FUM develops into a -plug-like structure. irb involucral bract, umbt umbellet, ilb involucellar bract, rafl radial flower, ryfl ray flower, sp sepal, st stamen, pt petal; cp carpel. Scale bars = 100 µm