Willowherb pollen. Coloured scanning electron micrograph (SEM) of the pollen grains of the rosebay willowherb (Epilobium angustifolium). The triangular wind-dispersed grains are in clusters of four. Pollen grains contain the male gametes. If a grain lands on the female part of a flower, it fertilizes its ovule. The fertilized ovule grows to become a seed. Magnification: x400 at 6x7cm size.