The complaint shall particularly describe the property sought to be partitioned, and shall set forth the title and rights of all parties interested therein and the extent of their respective interests, as far as known to the plaintiff. In case any person or persons interested are unknown to the plaintiff so that they cannot be named, or if the plaintiff does not know the share or quantity of interest of any party, or if any share or interest is uncertain or contingent or dependent upon some executory devise or provision, so that the same cannot be stated by the plaintiff, the facts shall be stated in the complaint and, if required by the rules of court, a supporting affidavit shall be furnished.