Sort (nested) XML with XSL and multiple hierarchy

i do have a treeview xml that i want to sort with xsl, but it seems i'm missing something:

The structure of my xml is something like this:

<treeview>
  <treenode>
    <caption>Directory Z</caption>
    <nodes>
      <treenode>
        <caption>File B</caption>
      </treenode>
      <treenode>
        <caption>File Z</caption>
      </treenode>
      <treenode>
        <caption>File A</caption>
      </treenode>
    </nodes>
  </treenode>
  <treenode>
    <caption>Directory G</caption>
    <nodes>
      <treenode>
        <caption>File F</caption>
      </treenode>
      <treenode>
        <caption>File O</caption>
      </treenode>
      <treenode>
        <caption>File B</caption>
      </treenode>
    </nodes>
  </treenode>
</treeview>

I tried the following xsl to perform a sorting:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://ift.tt/tCZ8VR">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes" />
  <xsl:template match="/*">
    <treeview>
      <xsl:apply-templates select="treenode">
        <xsl:sort select="caption" data-type="text" order="ascending"/>
        <xsl:sort/>
      </xsl:apply-templates>
    </treeview>
  </xsl:template>
  <xsl:template match="treenode">
    <xsl:copy-of select="."/>
    <xsl:apply-templates select="nodes/treenode">
      <xsl:sort select="caption" data-type="text" order="descending"/>
      <xsl:sort/>
    </xsl:apply-templates>
  </xsl:template>
</xsl:stylesheet>

I end up with the files being added to the root node, but i want the directories to be sorted ascending and the files in each directory descending.

Thanks for your help :)