SEC. 20. And be it further enacted, That where in a circuit court, a plaintiff in an action, originally brought there, or a petitioner in equity, other than the United States, recovers less than the sum or value of five hundred dollars, or a libellant, upon his own appeal, less than the sum or value of three hundred dollars, he shall not be allowed, but at the discretion of the court, may be adjudged to pay costs.