False colour scanning electron micrograph of pollen grains of a Marsh Woundwort. The outer walls (exine) have a netted ornamentation. When a pollen grain, containing the male gametes, lands on the stigma of a flower, it germinates. A pollen tube grows out from the pollen grain, down through the stigma, to the ovary. The male nuclei pass down this tube, fertilize the ovules & a seed is formed. Magnification: X971 at 35mm size.