Lime pollen. Coloured scanning electron micro- graph (SEM) of pollen grains from the small-leaved lime (Tilia cordata). The sculptured outer wall (or exine) of the grains plays a role in their dispersal by wind, water or insects. Pollen grains contain the male gametes of the plant which ferti- lise the female egg (or ovule) to form the plant's seeds. Wind-dispersed pollen may cause allergies and hay fever. Magnification: x1100 at 6x6cm size.