§ 1. ASPLENIUM proper. Indusium straight or slightly curved, attached to the upper side of the vein, rarely double.
[*] Small evergreen ferns; fronds pinnatifid, or pinnate only near the base.
1. A. pinnatífidum, Nutt. Fronds (3–6´ long) lanceolate, pinnatifid, or pinnate below, tapering above into a slender prolongation, "the apex sometimes rooting"; lobes roundish-ovate, obtuse, or the lowest pair long-acuminate; fruit-dots irregular, those next the midrib often double, even the slender prolongation fertile.—On cliffs and rocks, Penn. to Mo., and southward; very rare. July.—Resembles the Walking-Leaf (Camptosorus), but the veins are free. Stipes brownish, becoming green above, and so passing into the broad pale green midrib.
2. A. ebenoìdes, R. R. Scott. Fronds (4–9´ long) broadly lanceolate pinnatifid, below pinnate, the apex prolonged and slender; divisions lanceolate from a broad base, the lower ones shorter, often proliferous, as is the apex of the frond; fruit-dots much as in the last; stipes black and polished, as is the lower part of the midrib, especially beneath.—Limestone cliffs, Conn. and Penn., and southward; very rare, usually growing with Camptosorus and Asplenium ebeneum, of which Rev. M. G. Berkeley considered it a probable hybrid.
[*][*] Small evergreen ferns; the narrow fronds simply pinnate with numerous pinnæ.
[+] Pinnæ not auricled.
3. A. víride, Hudson. Fronds (2–5´ long) tufted, linear in outline, pale green, softly herbaceous; pinnæ roundish-ovate or ovate-rhomboid, short-stalked, crenately toothed (2–4´´ long), the midvein indistinct and forking; the slender stipe brownish and passing into a green herbaceous rhachis.—Shaded cliffs; northern New Eng., west and northward; rare. (Eu.)
4. A. Trichómanes, L. Fronds (3–8´ long) in dense spreading tufts, linear in outline, dark green and more rigid; pinnæ roundish-oblong or oval (3–4´´ long), entire or crenulate, rarely incised, unequal-sided, obliquely wedge-truncate at base, attached by a narrow point, the midvein forking and evanescent; the thread-like stipe and rhachis purple-brown and shining.—Shaded cliffs; common. July. (Eu.)
[+][+] Pinnæ more or less auricled.
5. A. párvulum, Mart. & Gal. Fronds upright (4–10´ high), narrowly linear-oblanceolate; pinnæ (2–6´´ long) rigid and thickish, mostly opposite, nearly sessile, somewhat deflexed, oblong, obtuse, entire or crenulate, auricled on the upper or both sides; sori rather few, as near the margin as the continuous midvein; stipe and rhachis black and shining.—Mountains of Va. to Mo., and southward.—Nearly intermediate between the last and the next.