sentences:  Because wood evolved long before shrubs and trees, it is likely that its original purpose was for water transport, and that it was only used for mechanical support later.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.