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The blackstem spleenwort or little ebony spleenwort, ''Asplenium resiliens'', is a species of fern native to the Western Hemisphere, ranging from the southern United States south to Uruguay, including parts of the Caribbean. Found on limestone substrates, it is named for its distinctive purplish-black stipe and rachis. A triploid, it is incapable of sexual reproduction and produces spores apogamously. First described by Martens and Galeotti in 1842 under the previously used name ''Asplenium parvulum'', the species was given its current, valid name by Kunze in 1844. Several similar species are known from the tropics; ''A. resiliens'' may have arisen from these species by reticulate evolution, but precise relationships among the group are not yet certain. ==Description== It is a small fern with pinnate fronds, growing in erect tufts, with a shiny black stipe and rachis (stem and leaf axis). Sterile and fertile fronds are similar in appearance. The roots are thin and wiry and do not proliferate to form new plants. The rhizome is short and erect, about in diameter. It has variously been described as sometimes branching or unbranched. It bears stiff filamentous, linear, or lance-shaped scales, which are blackish in color and obscurely clathrate (bearing a lattice-like pattern) or entirely black. The scales are long and wide, with untoothed, often brown, margins and long, drawn-out tips. Leaves are erect and borne in dense clumps, varying in size from long and from wide. The stipe (the part of the stem below the leaf blade) is straight and stiff and a glossy black to purplish-black in color. It may be smooth or bear scattered blackish-brown, threadlike scales long and tan, club-shaped hairs long which are appressed (lie flat against the stipe). The stipe measures long (rarely as long as ), and comprises one-tenth to one-quarter or one-third of the length of the blade. It is round in cross-section but slightly flattened adaxially and has indistinct wings on either side, or lacks them entirely. The leaf blade is linear in shape, sometimes slightly wider below the tip or just above the base. It measures from long and from wide, sometimes as wide as . It abruptly converges to a lobed, pointed tip and gradually tapers at its base. Unlike the related Palmer's spleenwort (''A. palmeri''), it does not form proliferating buds at the tip; however, the pinnatifid is often deciduous, leaving behind a naked rachis. The blade is hairless or bears scattered club-shaped hairs, long, beneath. The leaf tissue is often bluish-green and thick in texture, not quite leathery. The rachis, like the stipe, is rounded, blackish and shiny; it may be smooth or have a few of the tan hairs found on the stipe. The winging of the stipe extends up the rachis; it is variously described as taking the form of parallel, cartilaginous ribs, with a narrow, green, leafy wing, the ribs fusing into a wing towards the tip of the leaf, or a whitish to tan wing similar in dimensions to that of the stipe. The blade is cut into pinnae throughout its length, from 20 to 40 pairs per leaf. The pinnae are sessile (stalkless) or have minute stalks and are rectangular in shape, tapering slightly toward the tip. In North American and Mexican material, those in the middle of the leaf blade measure from in length (rarely as small as ) and from in width. In Guatemalan material, the pinnae typically measured from in length and from in width, the ratio of length to breadth being typically 1.5 to 2.5. Each pinna usually has an auricle at its base, pointing towards the tip of the blade; occasionally auricles pointing towards the base of the blade are also present. The edges of the pinnae are untoothed or have shallowly rounded teeth (or deep, rounded teeth in exceptional shade-grown specimens), and are often rolled under. The tips of the pinnae are blunt. The lower pinnae are widely spaced on the rachis, and reflexed downwards. Leaf veins are free (they do not rejoin one another) and are difficult to see; fertile veins are once-forking and do not terminate in hydathodes (prominent swellings). Fertile pinnae bear 2 to 6 pairs of sori (rarely as few as 1 pair or as many as 10), about in length, on both sides of the midrib; the sori are crowded at the edges and often merge together as they age. The indusia covering them are from long (rarely to ) and from wide, greenish or pale yellowish to whitish in color and opaque, with straight or slightly jagged edges. They are persistent after the spores mature, but may be hidden by the full sporangia. ''A. resiliens'' has a chromosome number of ''n'' = 2''n'' = 108 and produces 32 unreduced, round or egg-shaped spores per sporangium. 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 resiliens」の詳細全文を読む スポンサード リンク
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