Problem with richfaces tree menu

[safa]

Good Morning,
I'm trying to create a tree menu with richfaces, but the menu wasn't shown

My JSF code:

<a4j:form>
<rich:tree style="width:300px"
               value="#{parc.tree}" var="item">
               <rich:treeNode>
               
                    <h:outputText value="#{item.id}" />
               </rich:treeNode>
          </rich:tree>
     </a4j:form>

My ParcList Class:

@Name("parcList")
public class ParcList extends EntityQuery {

     private static final String[] RESTRICTIONS = {};

     private Parc parc = new Parc();

     @Override
     public String getEjbql() {
          return "select parc from Parc parc";
     }

     @Override
     public Integer getMaxResults() {
          return 25;
     }

     public Parc getParc() {
          return parc;
     }

     @Override
     public List<String> getRestrictions() {
          return Arrays.asList(RESTRICTIONS);
     }

     
     
     @In EntityManager entityManager;
     TreeNodeImpl parcTree=null;
     public void setTree(){
          
          List<Parc> parc = entityManager.createQuery("from Parc").getResultList();
          Iterator iter = parc.iterator();
          while (iter.hasNext()) {
               //iter.next();
               parcTree.addChild((Parc)iter.next(), parcTree);
          }
     }
     
     public List getTree(){
          List <Parc> parcs = (List<Parc>) parcTree;
          return parcs;
     }
     

}

and My entity class:

@Entity
@Table(name = "parc", schema = "public")
public class Parc implements java.io.Serializable {

     private int id;
     private AireProtegee aireProtegee;
}

I use seam 2.0.3

I really need your help,
thx