§ 20. Districts. The by-laws may provide for the division of the territory served or to be served by a cooperative into two or more districts for any purpose, including, without limitation, the nomination and election of directors and the election and functioning of district delegates. In such case the by-laws shall prescribe the boundaries of the districts, or the manner of establishing such boundaries, and the manner of changing such boundaries, and the manner in which such districts shall function. No member at any district meeting and no district delegate at any meeting shall vote by proxy or by mail.