Howe Bradley collected a number of specimens near Coal Creek, on Walden's Ridge in East Tennessee. Bradley sent some of them to Daniel Cady Eaton, who recognized it as a species distinct from A. montanum and named it for Bradley in an 1873 publication. While both Asa Gray and Eaton identified A. bradleyi as a hybrid intermediate between A. montanum and A. platyneuron, the English botanist R. Morton Middleton proposed in 1892 that it was identical or closely related to A. viride. This conclusion was based on the examination of forms growing in shade on the Cumberland Plateau which lacked color in the rachis, and was endorsed by contemporary Tennessee botanists such as Augustin Gattinger and Kirby Smith. This was rebutted in 1893 by Amos A. Heller, who pointed out that most collections of A. bradleyi had a dark stipe and that it possessed an auricle (the acroscopic pinnule) which A. viride lacked. Instead, Heller perceived in some of his specimens from the lower Susquehanna River affinities to A. montanum and A. pinnatifidum. Middleton, nevertheless, continued to maintain his theory of an affinity with A. viride, and speculated that A. bradleyi was not a hybrid, but an "intermediate" between A. viride and lanceolate spleenwort (A. obovatum ssp. lanceolatum). Edgar T. Wherry speculated at length on the hybrid origins of A. bradleyi and other Appalachian spleenworts in 1925, but the scheme he proposed was later found to be untenable, although he did recognize the contribution of A. platyneuron to its ancestry. Herb Wagner, in 1953, suggested instead that it was the hybrid of A. montanum and A. platyneuron, noting that Eaton and W. N. Clute had already made tentative suggestions along those lines. His cytological studies the following year showed that A. bradleyi was an allotetraploid, the product of hybridization between A. montanum and A. platyneuron to form a sterile diploid, followed by chromosome doubling that restored fertility. These findings were later supported by chromatographic analysis of flavonoid compounds. Chromatograms of A. bradleyi showed a combination of all the compounds found in A. montanum and all those in A. platyneuron. A. × wherryi showed the same pattern, as it also contains chromosomes from both of those species. A specimen of A. stotleri was subsequently shown to form the same chromatograms as well. This showed that it was not descended to A. pinnatifidum, whose chromatograms contain compounds inherited from walking fern (A.