This occurs on non-calcareous rocks in the Appalachians, Shawnee Hills and, especially, the Ozarks. It is largely tetraploid (2n = 144), derived from platyneuron and montanum (FNA 2). Hybrids of bradleyi with montanum (X wherryi Maxon) and pinnatifidum (X gravesii Maxon) are occasionally found in Ky. (Cranfill 1980; colls. at KY, Morehead, etc.). In some localities these hybrids are known but pure bradleyi has not yet been verified (MCRE, MORG, POWE).