Xpath expression for nested elements with same name

Hello,

This is my first post.  I have an XML document 

<svg>
 <g>
  <g id='match_this'>
   <g>
    <rect x="100" y="100" width="10" height="10" />
    <rect x="300" y="100" width="10" height="10" />
    <rect x="500" y="100" width="10" height="10" />
   </g>
  </g>
 </g>
</svg>

I would like to return all nodes that are descendents of <g
id='match_this'>.  Can you help with the path expression please?  I would
like to return the node set

   <g>
    <rect x="100" y="100" width="10" height="10" />
    <rect x="300" y="100" width="10" height="10" />
    <rect x="500" y="100" width="10" height="10" />
   </g>


Thanks, Simon