Ecological, Biosystematic, and Nomenclatural Notes on Scott's Spleenwort, X Asplenosorus ebenoides

Abstract

The best known and historically most interesting fern of the Appalachian region is the Scott's Spleenwort, xAsplenosorus ebenoides (Scott) Wherry (Alston, 1940; Weatherby, 1949), a bigeneric hybrid between Asplenium platyneuron and Camptosorus rhizophyllus. The Ebony Spleenwort, A. platyneuron (L.) Oakes, has tall, pinnately compound leaves with shiny, blackish midribs; its veins are simple and bear parallel sori. The Walking Fern, Camptosorus rhizophyllus (L.) Link, has attenuate, simple leaves with green midribs; its veins are reticulate and bear arching sori. Proliferous leaves of the Walking Fern bear a plantlet at their long and thread-like tip. The hybrid fern combines the parental characteristics in a spectacular and often highly asymmetric manner. The hybrid was first found near Philadelphia along the Schuylkill River around 1862 by a horticultural writer, Robert Robinson Scott, and has been known as Scott's Spleenwort ever since (Weatherby, 1949). Scott published a short description in Thomas Meehan's Gardener's Monthly in 1865 and called it Asplenium ebenoides (i.e., like ebeneum, the then-current synonym of platyneuron). However, Meehan in an editorial note suggested that it might be a hybrid, and the following year the British naturalist Rev. M. J. Berkeley proposed its parents correctly (Weatherby, 1949). A number of problems center around Scott's Spleenwort. There has been a question about the correctness of the epithet ebenoides. A fern considerd by some to be identical to it had been named Asplenium hendersonii by Houlston a decade and a half earlier than A. ebenoides. It was assumed that Scott's Spleenwort was a sterile hybrid because in the original locality it occurred singly with the parents. However, around 1874, Julia L. Tutwiler, a teacher, discovered a large population of Scott's Spleenwort in Rock Hollow, near in Hale Co., Alabama, a ravine later known to botanists as Havana Glen. This apparently fertile population grew on a conglomerate rock of