Some trees have lived many lifetimes, standing as silent witnesses to history. Some are remarkable for their age and stature; others for their usefulness. A bristlecone pine tree in California has outlived man by almost 4,000 years; a baobab tree in Australia served as a prison for Aboriginal prisoners at the turn of the twentieth century; and a major oak in England was used as a hiding place for Robin Hood and his men (or so the story goes...). The...