Developing flower of Antirrhinum majus

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 (brown) will develop into five sepals; a leaf-like protective covering for the bud. The pale purple 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., Photo by DR JEREMY BURGESS/SCIENCE PHOTO LIBRARY