Abstract:Pollen morphology of 31 species in 9 genera, belonging to subfadrily Hydrangeoideae, was examined by means of microscope and scanning electron microscope. The shapes of pollen grains of most species are subspheroidal and subprolate. Apertures basically with tricolporate, in Deinanthe caerelea it shows a reduced non-meridional furrow. Omamentaion of exine ranges from perforate with or without granules to apparent reticulate. Xirengeshoma shows similarity to the remainder of the subfamily. A particularly close relationship of Pileostegia and Schizophragma is indicated. Hydrangea shows great variation, and is closely linked to other genera, suggesting its central place of evolution in Hydrangeoideae. The present observation also indicates that generally, there is no clear cut discrimination of groups in Hydrangeoideae and they overlap each other complexly.
