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
Naked hiking Naked hiking Naked hiking, also known as naked walking or freehiking, is a sub-category of the modern form of social nudity, and involves the undertaking of walking activities while naked. In the United Kingdom, Stephen Gough, known as The Naked Rambler, received much media coverage for walking naked from Land's End to John o' Groats in 2003–2004 and again in 2005–2006. He was arrested and released several times during both his walks while in England, and was imprisoned in Scotland. Conversely to Gough's experiences, in 2005 and 2006 the European Alps were crossed naked during a one-week hiking tour, and