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Roots fibrous, not proliferous or proliferous and producing tiny plantlets. Stems erect, rarely long-creeping; scales basally attached, clathrate. Petioles not articulate. Blades 1–4-pinnate, of diverse size and shape. Indusia present. x = 36.

Distribution

Worldwide.

Discussion

Species ca. 700 (28 species, 3 nothospecies in the flora).

References

None.

Key

1 Blades simple, pinnatifid, or forked (sometimes with free pinnae at base), not pinnate throughout. > 2
1 Blades pinnate throughout or pinnatifid only in distal 1/3, pinnae undivided to 1–3-divided. > 8
2 Blades less than 2–3 mm wide, linear, frequently forking or with 1–3 small, narrow projections. Asplenium septentrionale
2 Blades more than 10 mm wide, linear-lanceolate to lanceolate, if lobed, segments resembling adnate pinnae. > 3
3 Veins anastomosing to form areoles; blades rooting at tip. Asplenium rhizophyllum
3 Veins free; blades with apical buds or not but not rooting at tip. > 4
4 Blades simple, linear to oblanceolate. > 5
4 Blades pinnatifid, elliptic, lanceolate, to deltate. > 6
5 Blades cordate at base; roots not proliferous. Asplenium scolopendrium var. americanum
5 Blades tapered at base; roots proliferous. Asplenium serratum
6 Petioles 1 cm or less, dull; stem scales 0.6–1 mm wide, sparsely denticulate. Asplenium dalhousiae
6 Petioles 1–10 cm, lustrous; stem scales less than 0.5 mm wide, entire. > 7
7 Petioles dark-pigmented only at base; blade narrowly deltate. Asplenium pinnatifidum
7 Petioles and proximal midrib darkly pigmented abaxially; blade oblong- lanceolate. Asplenium ebenoides
8 Blades 2–4-pinnate, with only largest pinnae divided to all pinnae divided. > 9
8 Blades 1-pinnate, pinnae undivided (except in some individuals of A. pumilum). > 18
9 Blades deltate-ovate, with 2–5 pairs of pinnae; pinnae generally deltate-ovate to obdeltate, rarely lanceolate to narrowly elliptic; color in living plants dull bluish green. Asplenium ruta-muraria
9 Blades ovate-lanceolate to linear, with 5–20 pairs of pinnae; pinnae linear to oblong; color in living plants shiny green. > 10
10 Delicate root proliferations usually present (commonly buried in mossy soil in crevices, but enabling clone formation); damp, shaded limestone; Florida. > 11
10 Delicate root proliferations absent or rare; mainly rock crevices; plants not in Florida. > 15
11 Spores uniform and normal. > 12
11 Spores of different sizes and shapes, malformed (irregular in size and shape). > 13
12 Blades oblong-lanceolate, mostly 2- pinnate; pinnae lanceolate to oblong- lanceolate. Asplenium cristatum
12 Blades narrowly lanceolate, 2–3- pinnate; pinnae ovate to ovate- deltate. Asplenium verecundum
13 Blades linear-lanceolate, s Florida. Asplenium ×biscayneanum
13 Blades oblong-lanceolate, c Florida. > 14
14 Medial pinnae pinnate throughout; pinnules mostly deeply notched apically. Asplenium ×curtissii
14 Medial pinnae pinnate only in proximal 1/2; pinnules mostly shallowly notched apically. Asplenium plenum
15 Buds at blade, pinna, and pinnule apices minute, scaly, dormant; Arizona. Asplenium exiguum
15 Buds absent; foothills and mountains in e United States and s Rocky Mountains. > 16
16 Petioles all pale green except at base. Asplenium montanum
16 Petioles dark reddish brown. > 17
17 Blades lanceolate to linear- lanceolate, 1–2-pinnate; proximal pinnae often somewhat reduced; e United States foothills and mountains. Asplenium bradleyi
17 Blades deltate-ovate to deltate- lanceolate, 2–3-pinnate; proximal pinnae usually largest; s Rocky Mountains. Asplenium adiantum-nigrum
18 Pinna pairs 1–2(–4); blades ovate-deltate, with fine nonglandular hairs on veins. Asplenium pumilum
18 Pinna pairs 5–35; blades mainly oblong to lanceolate, usually with glandular hairs or narrow hairlike scales on veins or blades glabrous. > 19
19 Pinnae with conspicuous basal auricles overlapping rachis; sori inframedial; leaves ± dimorphic, upright and tall, or spreading and short; plants often terrestrial. Asplenium platyneuron
19 Pinnae bases not overlapping rachis; sori medial to supramedial; leaves monomorphic; plants mainly on rock (epiphytic in A. auritum). > 20
20 Blades mostly 4–9 cm wide, linear- lanceolate to oblong-lanceolate. > 21
20 Blades mostly less than 3 cm wide, mainly linear. > 22
21 Blades linear-lanceolate, to 35 cm; pinna pairs 10–22, base with conspicuous acroscopic auricle; epiphytic on tree trunks. Asplenium auritum
21 Blades oblong to oblong-lanceolate, to 20 cm; pinna pairs 4–8, base with or without small acroscopic auricle; on mossy limestone. Asplenium abscissum
22 Sori 1(–3), mainly confined to basiscopic side of strongly asymmetric pinnae. Asplenium monanthes
22 Sori 4–10, on both sides of costa of nearly symmetric pinnae. > 23
23 Blade apex prolonged into whiplike extension of rachis terminating in bud. Asplenium palmeri
23 Blade apex not prolonged, terminal bud absent. > 24
24 Pinnae ovate, oblong-ovate, to rhombic, mainly 4–7 mm, length 1–2 times width. > 25
24 Pinnae oblong-lanceolate to oblong, mainly 6–10 mm, length 3–5 times width. > 28
25 Rachises dark reddish brown throughout. Asplenium trichomanes
25 Rachises dark in proximal 1/3–2/3 or only at base. > 26
26 Rachises dark in proximal 1/3–2/3; pinna margins entire to shallowly crenate. Asplenium adulterinum
26 Rachises dark only at base; pinna margins dentate-crenate. > 27
27 Pinnae with basiscopic 1/2 much reduced; blades mainly less than 1 cm wide; n North America. Asplenium trichomanes-ramosum
27 Pinnae nearly symmetric; blades mainly more than 1 cm wide; s Florida. Asplenium trichomanes-dentatum
28 Pinna margins deeply lobed, especially acroscopic and distal margins, cut 1/3 or more distance from margin to costa; s California. Asplenium vespertinum
28 Pinna margins nearly entire or shallowly crenate- dentate; se United States to e Arizona. > 29
29 Pinna margins nearly entire; sori supramedial; spores 32; widespread in s United States. Asplenium resiliens
29 Pinna margins ± shallowly crenate- dentate; sori medial to inframedial; spores 32 or 64; local in se United States. > 30
30 Pinna margins shallowly crenulate; auricle present at pinna base; veins obscure; spores 32 per sporangium. Asplenium ×heteroresiliens
30 Pinna margins serrate to crenate; auricle rudimentary or absent at pinna base; veins evident; spores 64 per sporangium. Asplenium heterochroum