The trustees may, out of any appropriation made for the support of the California State University, without at the time furnishing vouchers and itemized statements, withdraw a sum or sums necessary to be used by the academy to provide for the payment of expenses of any training cruise, which shall be paid to the master of the training vessel. The sum or sums so drawn for any training cruise shall, not later than 30 days following the termination of the training cruise be accounted for and substantiated by vouchers and itemized statements. Any unexpended balance of the sum or sums so withdrawn shall be returned to the appropriation from which originally withdrawn.