Section 21 Sanctioned forms of feu-charters, &c., to be modified.

In cases where by statutory authority or by judicial sanction forms of feu-charters, feu-contracts, feu-dispositions or contracts of ground annual have been sanctioned, and these forms contemplate the exaction of duplicands or other payments prohibited by this Act as regards future feus, it shall be lawful for the parties concerned, without the necessity for any sanction other than this Act, to modify as regards the future the said forms which have been sanctioned so as to make them comply with enactments and provisions of this Act, and it shall not be necessary in such modified forms to refer to this Act.