From Joomla! Documentation
The "API16" namespace is an archived namespace. This page contains information for a Joomla! version which is no longer supported. It exists only as a historical reference, it will not be improved and its content may be incomplete and/or contain broken links.
JTree is a class that allows you to create and walk through object-trees. Used in conjunction with the JNode class.
jimport( 'joomla.base.tree' );