(b) in any appeal to the Board from an order of the Registrar on an application for registration of a trade mark-
(i) which is not opposed, and the application is either refused by the Registrar or is accepted by him subject to any amendments, modifications, conditions or limitations, or
(ii) which has been opposed and the Registrar considers that his appearance is necessary in the public interest, and the Registrar shall appear in any case if so directed by the Board.