Asplenium montanum
| Mountain spleenwort | |
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| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta |
| Class: | Polypodiopsida/Pteridopsida (disputed) |
| Order: | Polypodiales |
| Family: | Aspleniaceae |
| Genus: | Asplenium |
| Species: | A. montanum |
| Binomial name | |
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Asplenium montanum Willd. |
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| Synonyms | |
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. It grows in small crevices in sandstone cliffs with highly acid soil, where it is usually the only vascular plant occupying that ecological niche. It can be recognized by its tufts of dark blue-green, highly divided leaves. The species was first described in 1810 by the botanist Carl Ludwig Willdenow. No subspecies have been described, although a discolored and highly dissected form was reported from the Shawangunk Mountains in 1974. Asplenium montanum is a diploid member of the "Appalachian Asplenium complex," a group of spleenwort species and hybrids which have formed by reticulate evolution. Members of the complex descended from A. montanum are among the few other vascular plants that can tolerate its typical habitat.
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. A. montanum 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 2 to 4 millimeters (0.1 to 0.2 in) 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 2 to 11 centimeters (0.8 to 4.3 in) 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 only at the very base of the stipe, which is slender and fragile, and lacks wings.
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