POLLEN MORPHOLOGY OF NORTH-AMERICAN COREOPSIS (COMPOSITAE-HELIANTHEAE)

The exomorphology of pollen grains of all North American species of Co reopsis have been thoroughly studied under the SEM for the first time with a view to contributing data to the ongoing studies on generic del imitation between Bidens and Coreopsis. The grains are echinate, trico lporate, isopolar, radially symmetrical, and spheroidal. The size of t he pollen grain is between 16.3-31.7 +/- 15.5-28.3 mu m and the length of the spine ranges between 3.5 and 6.8 mu m. No distinct differences in pollen morphological features between the sections of North Americ an Coreopsis were found. These results are also compared with previous findings on the pollen grains of African Bidens (incl. Coreopsis) and only few quantitative and qualitative differences in exomorphology we re detected.