The preference of voters shall be indicated by inserting a cross mark following either one or the other of the foregoing propositions, and said ballot shall have printed upon the face thereof instructions to the voters, worded as follows:'To vote for or against an increase in the number of directors of the .............. Irrigation District, a voter shall place a cross mark in the space at the right of the words expressing his wish either 'FOR' or 'AGAINST' such increase.'L. 45: p. 419, § 3. CSA: C. 90, § 487(3). CRS 53: § 149-3-6. C.R.S. 1963: § 150-3-6.