Massachusetts Constitution Amendments Art. XLVIII, Init., Pt. IV, § 2

If a proposal for a specific amendment of the constitution is introduced into the general court by initiative petition signed in the aggregate by not less than such number of voters as will equal three per cent of the entire vote cast for governor at the preceding biennial state election, or if in case of a proposal for amendment introduced into the general court by a member of either house, consideration thereof in joint session is called for by vote of either house, such proposal shall, not later than the second Wednesday in May, be laid before a joint session of the two houses, at which the president of the senate shall preside; and if the two houses fail to agree upon a time for holding any joint session hereby required, or fail to continue the same from time to time until final action has been taken upon all amendments pending, the governor shall call such joint session or continuance thereof.