Pollen grains. Coloured scanning electron micrograph (SEM) of various pollen grains. They display a great variation in their size, shape and surface texture. The outer wall (exine) is highly sculpted in many plants, for example the bright yellow grains at lower left. The sculpting might aid in dispersal of the pollen grains, by improving their adherence to pollinators. The characteristic surface of pollen grains is used by botanists to recognise and classify plants. Each pollen grain contains a male gamete (reproductive cell) that is intended to fertilise an egg or ovule (female gamete), and initiate the formation of a seed for a new plant. Magnification unknown.