Whenever any person interested in land as aforesaid shall be an infant, F1person of unsound mind, idiot, feme covert, or under any other legal disability, or beyond the seas, the guardian, trustee, committee of the estate, husband, or attorney respectively, or in default thereof such person as may be nominated for that purpose by the commissioners, and whom they are hereby empowered to nominate under their hands and seal, shall for the purposes of this Act be substituted in the place of such person so interested.