Scanning electron micrograph of a developing flower bud of the snapdragon, Antirrhinum majus. The picture shows a dissected bud, 0.6 mm in diameter. At this early stage, three concentric types of tissue can be seen. The outermost (yellow) will develop into five sepals; a leaf-like protective covering for the bud. The green tissues are the future petals of the flower, and the central red region will develop sexual organs - the stamens and style. The flower is zygomorphic; it has only one plane of symmetry - here, on each side of a central vertical axis. The sepals will all be of a similar shape at maturity, but the petals will not. The lower petals form a broad hinged landing platform for insects; the upper, a flag. Heavy insects (eg bumblebees) landing on the platform cause it to sink, enabling access to the sexual organs of the plant, resulting in pollination and seed formation.