Section 26. Said bond shall be executed by said person, partnership, association or corporation as principal, with a surety company as surety; or cash may be accepted in lieu of a surety company. The bond shall not be accepted unless it is approved by the state treasurer after having been examined and approved by the commissioner of banks. Upon its approval by the treasurer, it shall be filed in his office. Said bond may be cancelled at any time by the principal, by the surety company or by the state treasurer upon written notice by registered mail given by the principal, the surety company or the state treasurer to each of the others, said notice to state the effective date of the cancellation which shall not be sooner than thirty days from the date of the mailing of such notice.