Section 13. The annual meeting of the corporators of a mutual bank shall be held at a time as the by-laws direct. Special meetings may be held by order of the trustees or upon written request of at least 10 corporators addressed to the clerk who shall give notice of special meetings upon that order or request. In the absence or inability of the clerk to serve, the president or a vice president may give the notice required by this section. At least 7 days before the date of the meeting, written notice of the meeting shall be mailed to each corporator. The names of those present at a meeting shall be entered in the records of the corporation. A quorum shall consist of not less than 13 corporators or 25 per cent of the total number of corporators, whichever is greater; provided, however, that not more than 50 corporators shall be necessary to constitute a quorum.