[Zope] tree tag: how to find out if a folder is a leave

Hi Zopsters, I need to build a navigation tree that has has only the leaf-folders hyperlinked. (Two frame design: left frame navigation, right frame some kind of property page, but only for the folders that are leaves in the tree.) so: in the tree tag, how do I find out whether an element is a leaf or not? Any kind of help is extremely welcome. Regards, Heiko. -- Heiko Stoermer