False-colour scanning electron micrograph of a pollen grain of mimosa, Acacia dealbata, about 39 micrometres across. The pollen grain contains the male gametes which fertilize the ovules in the ovary of the flowering plant to form a seed. In Acacia, pollen grains regularly associate multiples of 4 to form compound grains or polyads. The compound grain shown here is a typical example of a 16-grain association in a more or less square arrangement. There are 8 centrally placed grains (4 on top visible here & 4 below not visible) & these are surrounded by 8 peripheral grains. Magnification: x640 at 35mm size. Original is BW print B786/142