--- a/src/treecms/memory/OnMemoryForest.java	Tue May 17 21:25:17 2011 +0900
+++ b/src/treecms/memory/OnMemoryForest.java	Sat May 21 04:46:00 2011 +0900
@@ -5,12 +5,12 @@
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 import treecms.api.Forest;
-import treecms.api.NodeData;
 import treecms.api.NodeID;
 import treecms.api.SingleNode;
 import treecms.api.Tree;
 import treecms.api.MonotonicTree;
 import treecms.tree.id.AbstractRandomNodeID;
+import treecms.tree.util.NodeData;
 
 /**
  * Forestのオンメモリ上の実装．
@@ -99,14 +99,14 @@
 	 * @return TreeEditor
 	 */
 	@Override
-	public MonotonicTree getMonotonicTree(SingleNode _node)
+	public MonotonicTree getMonotonicTree(Tree _tree)
 	{
-		Forest forest = _node.getForest();
-		if(forest != this){
+		Forest forest = _tree.getRoot().getForest();
+		if(forest != this || !(_tree instanceof OnMemoryTree)){
 			throw new IllegalArgumentException();
 		}
 		
-		return new OnMemoryMonotonicTree((OnMemoryNode)_node);
+		return new OnMemoryMonotonicTree((OnMemoryTree)_tree);
 	}
 	
 	/**