Introduction: The Challenge of Flowering Plant History

Abstract

Angiosperms are well known for their incredible diversity in species number, range of habitat, and morphology. Recent counts have shown that there are at least 234,000 described species of flowering plants in some 437 families (Thorne, 1992a). This number exceeds the total number of species of all other photosynthetic land plants and algae combined (Sporne, 1974; Prance, 1977). Not only do angiosperms dominate in number of species, they are also found in a far greater range of habitats than any other group of land plants. At their extremes they range from the tropics to the tundra, and from freshwater and marine environments to deserts. Not surprisingly, angiosperms also display an unparalleled range in form, from tiny plants in the Lemnaceae to huge trees in the Myrtaceae. Examples of their morphological variability can be found in stems (e.g., Carlquist, Chapter 4), flowers (e.g., Tucker and Douglas, Chapter 7), carpels (e.g., Taylor and Kirchner, Chapter 6), and pollen (e.g., Brenner, Chapter 5).