By gift, grant, devise or bequest, a city may take money or real, personal or mixed property in trust for the benefit of the pension fund. The care, management, investment and disposal of the body of the trust shall be vested in the officer or officers of the city for the time the council designates. The care, management and disposal shall be directed by ordinance and the body of the trust shall be governed by the ordinance, subject to the directions that are not inconsistent with the ordinance, as the settlor of the trust may prescribe.