Coltsfoot pollen on stigmas. Coloured Scanning Electron Micrograph (SEM) of pollen grains on the stigmas of Coltsfoot flowers Tussilago farfara. The pollen is coloured red on the stigmatic surfaces of each small flower. These pollen grains have sharp spines which get caught on an insect and are thus transferred when the insect goes to a different flower to feed. When the pollen grains, containing the male gametes, land on the stigma of a flower, they germinate. A pollen tube grows out and down through the stigma, to the flower ovary. Male gametes pass down the pollen tube to fertilize the ovules (eggs) and so produce the seeds. Magnification: x6 at 6x6cm size.