Section 31. A third person dealing with a trustee, pursuant to the provisions of section fifteen or twenty-six, may assume without inquiry the existence of trust powers and the proper exercise thereof by the trustee. A third person shall not be bound to inquire whether the trustee has power to act as trustee or is properly exercising trust powers, and a third person without actual knowledge that the trustee is exceeding or improperly exercising his powers shall be fully protected in dealing with the trustee as if the trustee possessed and was properly exercising the powers he purports to exercise. A third person shall not be bound to assure the proper application of trust assets paid or delivered to the trustee in his capacity as trustee.