Flowers: evolution and diversity

Summary

The angiosperms, Magnoliopsida (Angiospermopsida), are by far the most diverse group of plants that has ever existed with more than 240 000 different species. Flowers are extraordinarily diverse but a few evolutionary trends can be recognized. Many trends are related to the greater and greater specialization of insect pollination mechanisms: towards bilateral symmetry, fusion and elaboration of floral parts and the compound inflorescence. Others are related to changes in the number of seeds produced and their protection and dispersal: towards different kinds of placentation, the inferior ovary and different fruit types. Some taxa have become adapted for wind pollination, and highly specialized for this mode of reproduction (e.g. the grasses).