It shall be the duty of such drainage commissioners annually to levy an assessment sufficient for the payment of the coupons hereinbefore mentioned as they fall due.

[(42-2958) 1913, ch. 16, sec. 30, p. 58; reen. C.L. 168:55; C.S., sec. 4549; I.C.A., sec. 41-2558; am. 1935, ch. 55, sec. 2, p. 103.]