We give several new applications of the wreath product of forest algebras to the study oflogics on trees. These include new simplified proofs of necessary conditions fordefinability in CTL and first-order logic with the ancestor relation; asequence of identities satisfied by all forest languages definable inPDL; and new examples of languages outside CTL, alongwith an application to the question of what properties are definable in bothCTL and LTL.