Evolutionary history of plants phloem on the outside. Since xylem cells comprise dead, lignified tissue, subsequent rings of xylem are added to those already present, forming wood. The first plants to develop secondary growth and a woody habit, were apparently the ferns, and as early as the Middle Devonian one species, "Wattieza", had already reached heights of 8 m and a tree-like habit. Other clades did not take long to develop a tree-like stature. The Late Devonian "Archaeopteris", a precursor to gymnosperms which evolved from the trimerophytes, reached 30 m in height. The progymnosperms were the first plants to develop true wood, grown from
On the Movements and Habits of Climbing Plants 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." (1862) 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) The following comprise the chapters: 1. Twining plants 2. Leaf climbers 3 & 4.Tendril bearers 5. Hook and Root climbers. Inspired by reading an 1858