To avert the evil of an indefinite increase of the property in mortmain and perpetuity, it shall not be lawful for any religious, charitable, literary or scientific society, association or corporation, present or future, to accumulate income into capital or invested estate, so as that the clear annual value thereof, as regards future acquisitions with those now held, shall exceed the limitation hereinbefore contained, and as regards acquisitions now held by or for any such body, shall not exceed said annual amount, except as the property now held does or, being made more productive, may exceed such amount, but all such clear income, after such amount of capital or invested estate shall be attained, shall be expended annually in and for the purposes, uses and trusts upon and for which the property producing it is held; and if there be not objects within the intent of such purposes, uses and trusts sufficient to exhaust such income, it shall be the duty of such body or association holding such property to apply to the legislature for authority to expend the income thereof upon such practicable objects as shall most nearly conform to the intent of the uses and trusts upon which such property is held, and in default thereof such income as shall not be so expended in execution of its trust shall be paid into the treasury of the commonwealth: Provided, That this section shall not be taken as intended to apply to any corporation or trust, if any there be, placed by contract beyond such legislative requisition.