For the purpose of meeting disbursements for retirement allowances, pensions, annuities and other payments, there may be kept available cash, not exceeding ten per cent of the total amount in the several funds of the system, on deposit in any one or more banks or trust companies of the State, organized under the laws thereof or of the United States. The sum on deposit in any one bank or trust company shall not exceed twenty-five per cent of the paid up capital and surplus of the bank or trust company.