(1) All grants previously issued by the several boards of county commissioners under the authority of chapter 3293, 1881, Laws of Florida, shall be subject to provisions of s. 597.010, relating to the marking of such lands, the payment of rents, the cultivation of such lands and the forfeiture provisions. (2) Any grantee of lands referred to in subsection (1) shall mark such lands and begin cultivation thereof as set forth in s. 597.010, within 90 days after the effective date of this act. The rentals prescribed by s. 597.010, shall be payable immediately upon the effective date of this act and in accordance with the provisions of said section. (3) If any grantee shall fail to comply with the provisions of this act his or her grant shall become null and void and the lands shall return to the ownership and jurisdiction of the state.