[Zope] tree view in LocalFS

LocalFS has a property "Display in Tree View" which says: This controls whether the Local File System object will be displayed in the management tree and other instances of the <dtml-tree> tag. Indeed, checking this box causes the tree to appear in the left zope panel, but if I create my dtml method then the localFS can not be traversed in a dtml-tree. The localFS displays as a branch but there is no '+' to traverse it. Any thoughts? Thanks, David.