Odum owned Brightacre (a tract of land) in fee simple. He conveyed it "to Pike, his heirs and assigns; but if Farley shall be living 30 years from the date of this deed, then to Farley, his heirs and assigns." The limitation "to Farley, his heirs and assigns" is
valid, because Farley's interest is a reversion  valid, because the interest will vest, if at all, within a life in being.  valid, because Farley's interest is vested subject to divestment.  invalid.