This unusually large-leaved tetraploid (2n = 36) is widespread across North America, but rare to absent in most southeastern states (K). In Ky. it is known only from ravine forests under limestone or sandstone cliffs in Appalachian regions and along the Kentucky River Palisades. In Tenn. it is known only in or around the adjacent Cumberland Plateau (Ch). C. simplex has relatively large seeds (ca. 1.5-2.5 mm long), and is associated with archaeological sites of Woodland age. It does not seem to have been widely domesticated as in bushianum (Ford 1985), but especially large-seeded plants (ca. 2-3 mm) from the Great Plains have been segregated as var. standleyanum (Aellen) Fern. Curiously, a DNA sample identified as "C. gigantospermum var. standleyanum" was placed close to album, not hybridum, in the dendrograms of Fuentes-Bazan et al, (2012). C. simplex and C. murale have been recently placed by these authors in the new genus, Chenopodiastrum, but we await further assessment before accepting this change for the Ky. atlas..