Juncus dubius Engelm. Juncus dubius Engelm. in Trans. Acad. Sci. St. Louis 2: 459–460. 1868 sec. Villaseñor 2016=Juncus rugulosus Engelm. in Bot. Gaz. 6(6): 224-225. 1881 syn. sec. The Plant List 2013