Floral synorganisation without fusion in Geranium

Flowers of Geranium robertianum (Geraniaceae) are salverform with five separate accesses for pollinators to the nectar. Endress shows that each of these canals is formed by six organs out of four whorls without any fusion, but with synorganisation by the high degree of symmetry of the flower and by architectural reinforcement of the perianth organs. Obdiplostemony is involved in this synorganisation.