Your problem is exactly what the error message states. You are missing a 
root element. All of your elements from the xml are on the same node 
level. There is no parent node or root node to enclose them. Therefore 
the xml is not well formed. It should look more like this. (Just an 
example) 

<TheTree>
  <TreeNode></TreeNode>
  <TreeNode></TreeNode>
</TheTree>