The board may divide any issue of bonds authorized pursuant to this chapter into two or more series, and may fix different dates of issuance and different maturity dates for the bonds of each series. The bonds of each series shall mature serially in amounts to be fixed by the board, and the board shall fix a date not more than 10 years from the date of issuance of each series for the earliest maturity of such series and shall fix a date not more than 50 years from the date of issuance of each series for the final maturity of such series.