It shall be lawful for any heir of entail in possession of any entailed estate in Scotland who is or shall be entitled to sell, convey, and dispose of any portion of such entailed estate, or any right or interest therein, under the powers conferred by the M1Lands Clauses Consolidation (Scotland) Act, 1845, to sell and convey such portion of such entailed estate, or such right or interest therein, to the company who by the said Consolidation Act may be authorized to acquire the same, in consideration of an annual feu duty or a ground annual payable by such company to such heir of entail and his successors in the lands, or in the right or interest therein so conveyed, and that in the form prescribed by the said Consolidation Act with respect to conveyances in feu by parties entitled absolutely to grant the same.