The trustees of each Augustana Evangelical Lutheran congregation shall be elected by the ballot of such electors as are by the rules and regulations of such congregations competent to vote for trustees, on such day in each year as such rules and regulations prescribe and upon the notice required by the rules of the congregation, and shall be responsible to such congregations in the manner and to the extent required by such rules. Such trustees shall continue in office until others are elected to fill their respective places. They shall have power to convey the real estate held by them only when authorized by the vote of the congregation for whose benefit it is held, at a meeting warned for that purpose, according to the rules of the congregation; and such congregations are authorized to give the care of all their property to their trustees.