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FNA | Family List | FNA Vol. 2 | Aspleniaceae

1. Asplenium Linnaeus, Sp. Pl. 2: 1078. 1753; Gen. Pl. ed. 5, 485, 1754.

Spleenwort [Greek splen, spleen; thought by Dioscorides to be useful for treating spleen diseases]

Warren H. Wagner Jr.
Robbin C. Moran
Charles R. Werth

Asplenium trichomanes

Credit: Harvard University Herbaria

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.

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


1 Blades simple, pinnatifid, or forked (sometimes with free pinnae at base), not pinnate throughout.   (2)
+ Blades pinnate throughout or pinnatifid only in distal 1/3, pinnae undivided to 1–3-divided.   (8)
       
2 (1) Blades less than 2–3 mm wide, linear, frequently forking or with 1–3 small, narrow projections.   7 Asplenium septentrionale
+ Blades more than 10 mm wide, linear-lanceolate to lanceolate, if lobed, segments resembling adnate pinnae.   (3)
       
3 (2) Veins anastomosing to form areoles; blades rooting at tip.   4 Asplenium rhizophyllum
+ Veins free; blades with apical buds or not but not rooting at tip.   (4)
       
4 (3) Blades simple, linear to oblanceolate.   (5)
+ Blades pinnatifid, elliptic, lanceolate, to deltate.   (6)
       
5 (4) Blades cordate at base; roots not proliferous.   5a var. americanum
+ Blades tapered at base; roots proliferous.   6 Asplenium serratum
       
6 (4) Petioles 1 cm or less, dull; stem scales 0.6–1 mm wide, sparsely denticulate.   1 Asplenium dalhousiae
+ Petioles 1–10 cm, lustrous; stem scales less than 0.5 mm wide, entire.   (7)
       
7 (6) Petioles dark-pigmented only at base; blade narrowly deltate.   3 Asplenium pinnatifidum
+ Petioles and proximal midrib darkly pigmented abaxially; blade oblong- lanceolate.   2 Asplenium ebenoides
       
8 (1) Blades 2–4-pinnate, with only largest pinnae divided to all pinnae divided.   (9)
+ Blades 1-pinnate, pinnae undivided (except in some individuals of A. pumilum).   (18)
       
9 (8) 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.   30 Asplenium ruta-muraria
+ Blades ovate-lanceolate to linear, with 5–20 pairs of pinnae; pinnae linear to oblong; color in living plants shiny green.   (10)
       
10 (9) Delicate root proliferations usually present (commonly buried in mossy soil in crevices, but enabling clone formation); damp, shaded limestone; Florida.   (11)
+ Delicate root proliferations absent or rare; mainly rock crevices; plants not in Florida.   (15)
       
11 (10) Spores uniform and normal.   (12)
+ Spores of different sizes and shapes, malformed (irregular in size and shape).   (13)
       
12 (11) Blades oblong-lanceolate, mostly 2- pinnate; pinnae lanceolate to oblong- lanceolate.   25 Asplenium cristatum
+ Blades narrowly lanceolate, 2–3- pinnate; pinnae ovate to ovate- deltate.   31 Asplenium verecundum
       
13 (11) Blades linear-lanceolate, s Florida.   23 Asplenium ×biscayneanum
+ Blades oblong-lanceolate, c Florida.   (14)
       
14 (13) Medial pinnae pinnate throughout; pinnules mostly deeply notched apically.   26 Asplenium ×curtissii
+ Medial pinnae pinnate only in proximal 1/2; pinnules mostly shallowly notched apically.   29 Asplenium plenum
       
15 (10) Buds at blade, pinna, and pinnule apices minute, scaly, dormant; Arizona.   27 Asplenium exiguum
+ Buds absent; foothills and mountains in e United States and s Rocky Mountains.   (16)
       
16 (15) Petioles all pale green except at base.   28 Asplenium montanum
+ Petioles dark reddish brown.   (17)
       
17 (16) Blades lanceolate to linear- lanceolate, 1–2-pinnate; proximal pinnae often somewhat reduced; e United States foothills and mountains.   24 Asplenium bradleyi
+ Blades deltate-ovate to deltate- lanceolate, 2–3-pinnate; proximal pinnae usually largest; s Rocky Mountains.   22 Asplenium adiantum-nigrum
       
18 (8) Pinna pairs 1–2(–4); blades ovate-deltate, with fine nonglandular hairs on veins.   17 Asplenium pumilum
+ Pinna pairs 5–35; blades mainly oblong to lanceolate, usually with glandular hairs or narrow hairlike scales on veins or blades glabrous.   (19)
       
19 (18) Pinnae with conspicuous basal auricles overlapping rachis; sori inframedial; leaves ± dimorphic, upright and tall, or spreading and short; plants often terrestrial.   16 Asplenium platyneuron
+ Pinnae bases not overlapping rachis; sori medial to supramedial; leaves monomorphic; plants mainly on rock (epiphytic in A. auritum).   (20)
       
20 (19) Blades mostly 4–9 cm wide, linear- lanceolate to oblong-lanceolate.   (21)
+ Blades mostly less than 3 cm wide, mainly linear.   (22)
       
21 (20) Blades linear-lanceolate, to 35 cm; pinna pairs 10–22, base with conspicuous acroscopic auricle; epiphytic on tree trunks.   10 Asplenium auritum
+ Blades oblong to oblong-lanceolate, to 20 cm; pinna pairs 4–8, base with or without small acroscopic auricle; on mossy limestone.   8 Asplenium abscissum
       
22 (20) Sori 1(–3), mainly confined to basiscopic side of strongly asymmetric pinnae.   14 Asplenium monanthes
+ Sori 4–10, on both sides of costa of nearly symmetric pinnae.   (23)
       
23 (22) Blade apex prolonged into whiplike extension of rachis terminating in bud.   15 Asplenium palmeri
+ Blade apex not prolonged, terminal bud absent.   (24)
       
24 (23) Pinnae ovate, oblong-ovate, to rhombic, mainly 4–7 mm, length 1–2 times width.   (25)
+ Pinnae oblong-lanceolate to oblong, mainly 6–10 mm, length 3–5 times width.   (28)
       
25 (24) Rachises dark reddish brown throughout.   19 Asplenium trichomanes
+ Rachises dark in proximal 1/3–2/3 or only at base.   (26)
       
26 (25) Rachises dark in proximal 1/3–2/3; pinna margins entire to shallowly crenate.   9 Asplenium adulterinum
+ Rachises dark only at base; pinna margins dentate-crenate.   (27)
       
27 (26) Pinnae with basiscopic 1/2 much reduced; blades mainly less than 1 cm wide; n North America.   21 Asplenium trichomanes-ramosum
+ Pinnae nearly symmetric; blades mainly more than 1 cm wide; s Florida.   11 Asplenium trichomanes-dentatum
       
28 (24) Pinna margins deeply lobed, especially acroscopic and distal margins, cut 1/3 or more distance from margin to costa; s California.   20 Asplenium vespertinum
+ Pinna margins nearly entire or shallowly crenate- dentate; se United States to e Arizona.   (29)
       
29 (28) Pinna margins nearly entire; sori supramedial; spores 32; widespread in s United States.   18 Asplenium resiliens
+ Pinna margins ± shallowly crenate- dentate; sori medial to inframedial; spores 32 or 64; local in se United States.   (30)
       
30 (29) Pinna margins shallowly crenulate; auricle present at pinna base; veins obscure; spores 32 per sporangium.   13 Asplenium ×heteroresiliens
+ Pinna margins serrate to crenate; auricle rudimentary or absent at pinna base; veins evident; spores 64 per sporangium. ..   12 Asplenium heterochroum

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