Pollen grain. Coloured scanning electron micrograph (SEM) of a maize plant pollen grain (Zea mays). There is great variation in the size, shape and surface texture of pollen. The outer wall (exine) is highly sculpted in many plants, which may assist in dispersal. Each pollen grain contains a male gamete, which fertilises the eggs or ovules, initiating the formation of plant seeds. Magnification: x795 at 6x7cm size.