In its strict sense, this winter annual is largely restricted to lowlands of the central Mississippi and lower Ohio Valley, in Ark., Mo., Ill., Ind., and Ky. (K; Sewell & Vincent 2006; see also notes of K. Yatskievych at http:// www.mobot.org/ MOBOT/ Research/ curators/ kay.shtml). Sewell & Vincent (2006) have resurrected P. covillei Wats., a segregate with highly fragmented range: from Mo., Ill. and Ind. (Wabash Rv.); to Ohio (including Lawrence Co. adjacent to Ky.) and W.Va.; to Md., Va. and N.C. It is expected in Ky., and differs from ranunculacea as follows: hairs at mid-stem sparse, mostly appressed/strigose, rarely spreading (versus dense, mostly spreading/pilose, some retrorse), plus a few glands <2 mm tall (versus dense and mostly >2 mm); terminal leaflets subtending inflorescence with acute-cuneate bases (versus obtuse-truncate); 2n = 28 (versus 12). Habitats are similar, typically on highly fertile soils in subhydric to mesic forests on floodplain terrace or toe-slopes.