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''Asplenium montanum'', commonly known as the mountain spleenwort, is a small fern endemic to the eastern United States. It is found primarily in the Appalachian Mountains from Vermont to Alabama, with a few isolated populations in the Ozarks and in the Ohio Valley. First described in 1810, it grows in small crevices in sandstone cliffs with highly acid soil. It can be recognized by its dark blue-green, highly divided leaves. ''Asplenium montanum'' is the ancestor, through hybridization, of several other ferns of similar habitat. ==Description== ''Asplenium montanum'' is a small, evergreen fern which grows in tufts. The leaves are bluish-green and highly divided, proceeding from a long and often drooping stalk. It is monomorphic, with no difference in form between sterile and fertile fronds. The horizontal rhizomes, which are about 1 millimeter across, may curve upward. They are not branched, but as new plants can form at root tips, a tightly packed cluster of stems may give the appearance of branching. The rhizomes are covered in dark brown, narrowly triangular scales, from long and from 0.2 to 0.4 millimeters across, with untoothed edges. They are strongly clathrate (bearing a lattice-like pattern). The stipe (the portion of the stem below the leaf blade) is dark brown to purplish-black and shiny at the base, gradually turning dull green as it ascends to the leaf blade. The stipe is from long, and may be from 0.5 to 1.5 times the length of the blade. Dark, narrowly lance-shaped scales and tiny hairs are present at the very base of the stipe only; it is slender and fragile, and not winged. The leaf blade is thick and hairless, and of a dark blue-green color; the rachis (leaf axis), like the stipe, is a dull green, with occasional hairs. The blade is triangular or lance-shaped, with a squared-off or slightly rounded base and a pointed tip. It ranges from long and from wide, occasionally as much as . The blade varies from pinnate-pinnatifid to bipinnate-pinnatifid; that is, it is cut into lobed pinnae, and sometimes the pinnae themselves are cut into lobed pinnules. There are four to ten pairs of widely spaced pinnae per leaf, each of which is triangular to lance-shaped, with coarse incisions in the edges, which cut them into pinnules or deep lobes, and a rounded to angled base. The pinnules are indented, but not further cut. The longest pinnae are those nearest the base of the leaf, which range from long and from across. The veins in the leaf do not form a meshwork, and are obscure. On fertile fronds, from 1 to 15 elliptical or narrow sori can be found on each pinna. They are 0.5 to 1.5 millimeters long, covered by translucent, pale tan indusia with somewhat jagged edges. Each sporangium holds 64 spores. The species has a chromosome number of 2''n'' = 72 in the sporophyte; it is a diploid. The dark bluish-green color and the widely spaced, deeply cut and indented pinnae differentiate ''A. montanum'' from most related species. The pinnae of Bradley's spleenwort (''A. bradleyi'') are toothed and less deeply cut, and the dark color of the stipe continues partway up the rachis in that species. Wall-rue (''A. ruta-muraria'') has a green stipe, and its pinnae have longer stalks and are broadest near the tip. Wherry's spleenwort (''A. × wherryi''), a hybrid between Bradley's spleenwort and mountain spleenwort, is intermediate between its parents. When compared with mountain spleenwort, the blade of Wherry's spleenwort is lance-shaped, rather than triangular; the upper parts of the blade are not as deeply cut; and the dark color of the stipe extends to the beginning of the rachis. 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 montanum」の詳細全文を読む スポンサード リンク
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