If on any such day the plaintiff only appear, the Collector, upon proof that the summons or proclamation has been duly served according to the provisions of this Act, shall proceed to examine the plaintiff or his agent, and after considering the allegations of the plaintiff, and any documentary or oral evidence adduced by him, may either dismiss the case or postpone the hearing of it to a future day for the attendance of any witness the plaintiff may wish to call, or may pass judgment ex parte against the defendant.