A testator by his will directed his executor to pay to or permit his wife to receive the rents and profits of or to otherwise enjoy his real estate for her life, with power to the executor, with the consent of the wife, to lease the real estate. The rents and profits were to go to two sons of the testator after the death of the wife, and upon the death of the surviving son the executor was directed to sell the real estate and to pay the proceeds to the Alfred Hospital.