This often overlooked species ranges widely across southeastern states, and is most common along larger rivers. It typically occurs on poorly drained, clayey, base-rich alluvial soil, in contrast to grisea and (especially) amphibola. C. corrugata has recently been discovered in Ky. (Naczi et al. 2002), and more colls. of the amphibola group need to be reviewed. Though often confused with grisea and amphibola (e.g. Cr), corrugata is clearly a separate species; 2n = 58-62 versus 52-56 (FNA 23). Its perigynia are relatively short (ca. 3.9-4.5 mm versus 4.2-5 mm), with the achene widest at ca. 70% from base (versus 60%). Its blades tend to be narrower (mostly 4-5 mm versus 4-7 mm) and its basal sheaths are more consistently purple. Also, its perigynia are distinct from those of amphibola (but not grisea) in their broader shape (l/w ca. 1.7-2.3 versus 2.5-3.1),