Section 89. Any city or town committee shall, at the written request of fifty voters, members of its party, call caucuses of said party to determine by ballot whether the provisions of law for the use of official ballots shall be adopted. The notice of said caucus shall state the purpose for which it is called, the place, the day, and the hour, not earlier than six o'clock and not later than half past seven o'clock in the evening, of holding said caucus. It shall be issued at least seven days prior to the day named therefor, and shall be published at least twice in one or more local newspapers, if any, and shall be posted in at least five public places in each ward or town. The polls shall be kept open at least one hour. If said caucuses shall vote to adopt said provisions, all caucuses of said political party in said city or town shall thereafter be called and conducted accordingly.