A relative path expression like richtext/par selects downwards from the current node. The current node is the one that the for-each is currently processing. That's a <par> element, and there aren't any richtext elements as children of a <par>, so it selects nothing.
Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer's Reference