Asplenium bradleyi, commonly known as Bradley's spleenwort or cliff spleenwort, is a rare epipetric fern of east-central North America. Named after Professor Frank Howe Bradley, who first collected it in Tennessee, it may be found infrequently throughout much of the Appalachian Mountains, the Ozarks, and the Ouachita Mountains, growing in small crevices on exposed sandstone cliffs. The species originated as a hybrid between mountain spleenwort (Asplenium montanum) and ebony spleenwort (Asplenium platyneuron); A. bradleyi originated when that sterile diploid hybrid underwent chromosome doubling to become a fertile tetraploid, a phenomenon known as allopolyploidy. Studies indicate that the present population of Bradley's spleenwort arose from several independent doublings of sterile diploid hybrids. A. bradleyi can also form sterile hybrids with several other spleenworts. While A. bradleyi is easily outcompeted by other plants in more fertile habitats, it is well adapted to the thin, acidic soil and harsh environment of its native cliffs, where it finds few competitors. Its isolated situation on these cliffs protects it from most threats, but quarrying and mining of the cliffs, rock climbing, and other activities that disturb the cliff ecosystem can destroy it. Description Asplenium bradleyi is a small fern with dark green, pinnate-pinnatifid to bipinnate fronds. These form evergreen, perennial tufts. Notable characteristics are the dark stem, whose color extends well up the axis of the leaf blade, a deeply cut acroscopic lobe or pinnule at the base of each pinna, and toothed pinna edges. However, some of these characteristics are variable, and may not be observed in all individuals of A. bradleyi. Some specimens have rounded, rather than toothed edges and others lack dark coloration throughout most of the stem. The fronds are monomorphic, the sterile and fertile fronds appearing the same size and shape. Its rhizomes (underground stems) are short and parallel to the ground, or sometimes curving upwards, so the fronds spring up in a cluster. The rhizome is about in diameter, covered with narrowly triangular scales that are dark reddish to brown and strongly clathrate (bearing a lattice-like pattern). The scales are long and 0.2 to 0.4 millimeters wide, with untoothed or shallowly toothed edges. The stipe (the stalk of the leaf, below the blade) is upright, long, occasionally as much as . It lacks wings, and is reddish- to purplish-brown and shiny. It is one-third to three-quarter times the length of the blade. Small brown scales at the base of