The Department of Revenue may employ a secretary and such other persons as experts, engineers, stenographers, clerks, or assistants as may be necessary for the performance of the duties which may be required of said department subject to the provisions of the Merit System. All compensation for the expenses of said department shall be paid out of the appropriation made for the annual expenses of the Department of Revenue or out of the fund or funds out of which said expenses are properly payable upon warrants drawn by the Comptroller upon said fund or funds.