A century of research on heterostylous plants has passed since the publication of Charles Darwin's book "The Different Forms of Flowers on Plants of the Same Species" in 1877 summarizing his extensive observations and experiments on these complex breeding systems involving genetic polymorphisms of floral sex organs. Since then heterostylous plants have provided a rich source of material for evolutionary biologists and today they represent one of the classic research paradigms for approaches to the study of evolution and adaptation. The present book is the first modern and comprehensive accont of the subject. In 10 chapters it is concerned with the evolution, genetics, development, morphology, and adaptive significance of heterostyly. Broad syntheses of research on heterostyly as well as new theoretical ideas and experimental data are included.