The state treasurer shall, upon the warrant of the state comptroller, pay the fees and mileage of witnesses called, the compensation of legal and clerical assistance employed and the expenses of the sergeant at arms of either house in the execution of warrants pursuant to section 52:13-2 of this title, when the same shall be certified as correct and necessary by the chairman of the committee under whose authority and by whose order the same shall have been incurred, but only when the chairman’s certificate has received the approval of the governor.