I. caroliniana I. engelmannii var. caroliniana I. engelmannii var. valida
Isoetes valida, commonly known as the strong quillwort or true quillwort, is an aquatic pteridophyte native to eastern North America. It is found primarily in the Appalachian Mountains from Pennsylvania south to Alabama and Georgia. In addition, one collection of the plant was made in a railway ditch in Wilmington, Delaware in the 1860's, but this was most likely an accidental introduction.[2][3]
^ Taylor, W. Carl; Luebke, Neil T.; Britton, Donald M.; Hickey, R. James; Brunton, Daniel F. (1993), "Isoetes caroliniana", in Flora of North America Editorial Committee, eds. 1993+, Flora of North America, 2, New York & Oxford: Oxford University Press