intros t succs in_t.
elim in_t; clear in_t succs.
intros succs.
simpl in |- *.
apply le_n_max1.
intros t1 succs in_t le_t.
apply le_trans with (height_forest succs).
assumption.
simpl in |- *.
apply le_n_max2.
Qed.

Lemma My_Tree_ind :
forall P : Tree -> Prop,
(forall (a : A) (succs : Forest),
(forall t : Tree, In_Forest t succs -> P t) -> P (node a succs)) ->
forall t : Tree, P t.