private void initChildren()
  {
    if ( children == null )
      this.children = new ArrayList<TreeItem>();
    childSpanElement = DOM.createElement( "ul" );
    childSpanElement.setClassName( NavigationTreeResources.INSTANCE.css().childSpan() );
    if ( !getText().equals( "" ) )
    {
      if ( this.open )
      {
        getElement().addClassName( NavigationTreeResources.INSTANCE.css().treeItemOpen() );
        getElement().removeClassName( NavigationTreeResources.INSTANCE.css().treeItemClosed() );
      }
      else
        getElement().addClassName( NavigationTreeResources.INSTANCE.css().treeItemClosed() );
    }

    DOM.appendChild( getElement(), childSpanElement );

  }