Section 21. A company or corporation, public or private, or quasi corporation, or unincorporated association, or the managers of any trust, or any transfer agent, registrar or other agent of such company, corporation, quasi corporation, unincorporated association or managers, shall not be bound to see to the execution of any trust, express, implied or constructive, to which any of its shares, bonds or securities are subject, or to ascertain or inquire whether the trust authorizes a transfer thereof by the holder, but this section shall not be a protection against liability for participating with actual knowledge in a breach of trust, and the fact that the trust is of record shall not constitute such actual knowledge.