function toggleBranch (item_id) {
  var imgObj=document.images['img_'+item_id];
  if (imgObj.src.indexOf('expanded')!=-1) imgObj.src=imgObj.src.replace(/expanded/gi,'collapsed');
  else if (imgObj.src.indexOf('collapsed')!=-1) imgObj.src=imgObj.src.replace(/collapsed/gi,'expanded');
    toggleLayerDisplay('div_'+item_id);
}