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''Asplenium × boydstoniae'', commonly known as Boydston's spleenwort, is a rare, sterile, hybrid fern. It is formed by the crossing of Tutwiler's spleenwort (''A. tutwilerae'') with ebony spleenwort (''A. platyneuron''). The hybrid was produced in culture in 1954. It was not discovered in the wild until 1971, when it was found by Kerry S. Walter at Havana Glen, Alabama, the only known wild site for Tutwiler's spleenwort. Walter named it for Kathryn E. Boydston, an expert in fern culture. Except for the tip of its leaf blade, it largely resembles its ebony spleenwort parent. ==Description== ''Asplenium × boydstoniae'' is a small fern, similar to ebony spleenwort. The stem is a shiny dark brown, its color extending almost to the tip of the leaf blade, where it becomes green. Most of the blade is cut into pinnae, but it has an elongated, lobed tip. The fronds of ''A. × boydstoniae'' can be up to or long and or wide. The stipe (the part of the stem below the leaf blade) is long in medium-sized specimens and a glossy dark brown in color. Overall, the blade is lance-shaped, and truncated at the base. It is pinnately cut, having from 15 up to 27 pinnae, or from 25 to 35 in larger, cultivated specimens, on each side of the rachis (leaf axis). The tip of the blade is elongated, with the pinnae diminishing into fused lobes and then curved edges before reaching the acute tip. The dark glossy color of the stipe extends into the rachis, going about seven-eighths of the way up the length of the frond (including the stipe), extending further along the underside of the rachis than the upper side. The pinnae are sessile (stalkless), and may have a variety of shapes: roughly triangular, with one side distinctly longer than the other, lance-shaped, or slightly curved. In specimens produced in culture, the pinnae were quite regular in size (that is, similar in size to their immediate neighbors) and in shape, while they were more irregular in wild specimens. Illustrations show a small auricle at the base of each pinna, pointing towards the blade tip. Nonviable spores are borne in irregularly placed sori up to long. The sporophyte is triploid and has a chromosome number of 108. The literature does not discuss whether the species possesses the frond dimorphism typical of its parent ''A. platyneuron''. ''A. × boydstoniae'' can potentially be confused with other ''Asplenium'' hybrids and orthospecies (non-hybrids) in the Appalachian ''Asplenium'' complex. Among orthospecies, it is most similar to ''A. platyneuron'', from which it can be distinguished by its elongated blade tip, the green color on the apical one-eighth of its rachis, and, microscopically, by its abortive spores. It is similar to two other hybrids in the complex, Graves' spleenwort (''A. × gravesii'') and Kentucky spleenwort (''A. × kentuckiense''). In both of these, the pinnae have short stalks, rather than being sessile; the pinnae are fewer, typically from 5 to 12 rather than 25 or more; and the dark color of the stipe and rachis extends only halfway up the frond. It is easily distinguished from ''A. tutwilerae'', which has fewer pinnae which are more pointed and dramatically irregular, and a longer stipe and shorter leaf blade. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Asplenium × boydstoniae」の詳細全文を読む スポンサード リンク
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