The association may establish through its bylaws various subdistricts within the grazing district. When subdistricts are so established, one director of the association must be elected from each subdistrict by the majority vote of the members therein who are eligible to vote. If subdistricts are not established by the association, one director must be elected from each congressional township in the district by the majority vote of the members in such township who are eligible to vote. However, at the discretion of the membership of the association, all directors may be elected at large.