It is now generally assumed that there are somewhere between 220,000 and 420,000 species of vascular plants globally, and they are prominent in nearly all terrestrial ecosystems and make up the major part of the biomass. We do not yet know the current distribution of plant diversity, how it came about or how it is maintained, but considerable amount of research is going on in these fields, both on local, regional and global scales. Other research questions of great interest for the understanding of biodiversity are related to origin of diversity in major plant families; These questions are addressed in this book. It contains the proceedings of an international plant biodiversity symposium held at the Royal Danish Academy of Sciences and Letters in Copenhagen, Denmark, 25-28 May, 2003 and has 30 contributions from leading researchers or research groups from many parts of the world. Together, the book reflects the state-of-the-art in plant biodiversity research, particularly in the tropics.