In any irrigation district, organized under the laws of the state of Idaho, having three (3), five (5) or seven (7) directors, whenever a petition amounting to fifty per cent (50%) of the votes cast at the last annual election within the district, shall be filed with the board of directors of such district asking for an election within the district, for the purpose of increasing or decreasing the number of directors of such district, such board of directors shall thereafter immediately call an election for the purpose of deciding the question: provided, that the petition shall recite that each signer thereof is a legal voter, or land holder within such district and the signatures thereupon are verified by the person or persons circulating the same: provided, that the petition shall specify the number of directors demanded, which shall be three (3), five (5) or seven (7): provided, that such petition shall represent not less than twenty-five per cent (25%) of the area of the lands within such district as shown by the records of the district.