Following the Origin of Species Darwin set out to produce evidence for his theory of natural selection. Initially Darwin spent much time in studying plants to achieve this aim. This book stands second in line to his first work on plants, On the various contrivances by which British and foreign orchids are fertilised by insects. This work is subdivided into chapters concentrating on a particular type of climber which he divided into four main classes but Darwin, in this volume, concentrates on the two main classes, the twining plants and the leaf climbers (divided into two sub-divisions: leaf climbers and tendril bearers)