public Tree(UniversePool pool,Java3dPlugin plugin) {
_pool = pool;
_plugin=plugin;
_clipBoard=new ClipBoard();
_undoManager = new UndoManager();
_undoHandler = new UndoHandler(_undoManager);
_rootNode = new RootNode(this, null, false);
_treeModel = new DefaultTreeModel(_rootNode);
setModel(_treeModel);
setCellRenderer(new TreeCellRenderer());