Mo. Rev. Stat. § 362.640

Each bank and trust company which is to be a party to the merger or to the consolidation shall, upon being first authorized by its board of directors by the affirmative vote of a majority of all the members of the board, enter into an agreement with the other banks and trust companies which are to be parties to the merger or to the consolidation providing for the merger or the consolidation on the terms and conditions therein set out. The agreement shall be in writing, and executed and acknowledged under the respective seals of the banks and trust companies as are parties thereto. The execution and acknowledgment shall be in such form as now or hereafter required by law for execution and acknowledgment of instruments conveying real estate.