The executive department shall consist of a governor, secretary of state, auditor, treasurer, commissioner of agriculture and attorney general, who shall be ex officio reporter of the court of appeals. Their terms of office shall be four years, and shall commence on the first Monday after the second Wednesday of January next after their election. They shall reside at the seat of government during their terms of office, keep there the public records, books and papers pertaining to their respective offices, and shall perform such duties as may be prescribed by law.