68.06 Actions upon negotiable and other instruments; consideration, etc.—All bonds, notes, covenants, deeds, bills of exchange, and other written instruments not under seal have the same force and effect (so far as the rules of pleading and evidence are concerned) as bonds and instruments under seal. The assignment or endorsement of any instrument vests the assignee or endorsee with the same rights, powers, and capacities as were possessed by the assignor or endorser. The assignee or endorsee may bring action thereon. It is not necessary for the plaintiff in any action on an instrument assignable by law to allege the consideration on which the instrument was given or on which the assignment or endorsement was made nor to prove the consideration or the execution of the instrument, unless it is denied by the defendant under oath. An executor or administrator may deny the execution or consideration by answer not under oath.