[pstricks] Nested psTree environments

[E. Krishnan]

I find that with "treemode" set to "L" or "R" the code 

  \begin{psTree}{\Tr{Node1}}
    \begin{psTree}{\Tr{Node2}}
      \Tr{Node3}\Tr{Node4}
    \end{psTree}
  \end{psTree}  

gives the error

  ! Extraneous space in tree successors.
  \@pstrickserr ... immediate help.}\errmessage {#1}
                                                  \endgroup
while

  \begin{psTree}{\Tr{Node1}}
    \begin{psTree}{\Tr{Node2}}%
      \Tr{Node3}\Tr{Node4}
    \end{psTree}%
  \end{psTree}  

and also 

   \psTree{\Tr{Node1}}
     \psTree{\Tr{Node2}}
       \Tr{Node3}\Tr{Node4}
     \endpsTree    
   \endpsTree

works OK.  There's no problem with any of these for upward or downward 
trees. 

Can somebody explain this?

-- 
Krishnan