Flowering plants now dominate the terrestrial ecosystems of the planet, and there are good reasons for supposing that the flower itself has been a major contributing factor to the spread of the Angiosperms. Although the Angiosperm flower is based on four whorls of organs – petals, sepal, stamens and carpels – the 300 000 odd species exhibit a huge array of different floral morphologies. Consider, ., the humble periwinkle flower and contrast it with the complex passion flower. Since the early 1990s, the powerful tools of the molecular biologist have been applied to the study of the control of Angiosperm flower development. Two plant species, Antirrhinum majus.
