This widespread southeastern species generally occurs in woods with damp medium-acid soils, especially on seeping slopes and terraces. A. angustum (Willd.) K. Presl. is a closely related northeastern member of the felix-femina complex, with more robust, elliptic (versus subdeltoid) fronds, more glandular rachises and more dark-scaly stipes. It is reported adjacent to Ky. from Va. to Ohio to Mo. (PL), but not clearly present in Ky. (Cranfill 1980; FNA 2; W). A few plants in Appalachian regions are referable to forma subtripinnatum (following F).