Both principal and interest of said bond[s] shall be payable in lawful money of the United States, at the office of the state treasurer, or at such other place as may be designated in said bonds and in the coupons attached thereto, at the option of the holder. The principal of said bonds shall be made to mature in annual installments, to begin not later than two years from the date of said bonds.

The state board of finance shall, by resolution duly adopted, fix the schedule of maturities of principal to the end that total annual principal and interest requirements shall be approximately equal in each year when any of the said bonds mature, except that the total requirement for principal and interest in the last year in which any of said bonds mature, may exceed the average of the annual requirements for principal and interest in prior years during which bonds mature, by not exceeding twenty-five percent.