Exine architecture and function in some lythraceae and sonneratiaceae

The pollen morphology of selected species of Crenea, Lagerstroemia, Lafoensia and Diplusodon (Lythraceae) and of Sonneratia (Sonneratiaceae) is compared from a functional point of view. From a basically tricolporate type, multiplication of colpi, reduction of colpi, development of meridional ridges, development of polar caps, differentiation of pores and reduction of pores have led to partly diverging, partly converging structural types which are interpreted as adaptation to controlled harmomegathy. In some species of Lagerstroemia with dimorphic stamens, the exine of the pollen produced by the feeding anthers shows a specialized structure, which enables the pollen grain to retain moisture and become sticky. For Sonneratia the fossil record allows a check on the postulated evolutionary trends.