The Governor may, by warrant under his hand, from time to time, direct any of the Commissioners or Corporations in whom any of the said lands are vested, to set aside so much of the said lands for settlement and lease under this Act as he shall think fit, until the end of the next session of the General Assembly, but not exceeding in the whole twenty thousand acres, and may direct the lands so set aside to be subdivided for leasing into allotments not exceeding three hundred and twenty acres each, and may thereupon, by Proclamation, declare that such lands are open for leasing under this Act.