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17. Adiantum Linnaeus, Sp. Pl. 2: 1094. 1753.
铁线蕨属 tie xian jue shu
Authors: Youxing Lin, Jefferson Prado & Michael G. Gilbert
Plants terrestrial or epilithic, medium-sized or small; outlines highly variable. Rhizomes short and erect, or long and creeping, with siphonostele, covered with scales; scales brown or black, lanceolate, thick in texture, usually entire. Fronds monomorphic, whorled and clustered, scattered in 2 rows or compact, not articulate; stipe black or reddish brown, glossy, fine and rounded, hard, with 1 or 2 vascular bundles and combined into 1 upward; lamina mostly 1-3- or more pinnate or 1-3-dichotomous with pedate branches, rarely reduced to solitary entire and orbicular-flabellate pinnule, herbaceous or papery, less often leathery or membranous; rachises, costae, and stalks same color as stipe; pinnules sometimes with articulate stalk, ovate, flabellate, orbicular-flabellate, or dimidiate, margins serrate, lobed, or entire, usually deciduous when dried; veins free, reaching margins, simple or dichotomously forked, often radiate [rarely anastomosing (Hewardia)], usually visible on both surfaces of lamina. Sori borne on veins of recurved, membranous margins (false indusium); false indusium orbicular, reniform, lunate, ± rectangular, or oblong, free or continuous, upper margins forming deep sinus, retuse or truncate. Sporangia globose, long stalked, annuli erect; mostly consisting of 18-28 incrassate cells. Spores yellowish, tetrahedral, trilete, transparent, smooth. x = 15(30), 29.
More than 200 species: from cold temperate zone to tropics, most in South America; 34 species (16 endemic) in China.
The following species could not be treated here because no material was seen by the present authors: Adiantum menglianense Y. Y. Qian (Acta Bot. Austro Sin. 8: 37. 1992) and A. ornatum Ching (Bull. Fan Mem. Inst. Biol., Bot. 11: 55. 1941).
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| 1 |
Fronds each with a single suborbicular or orbicular-reniform pinnule. |
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1 A. reniforme |
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Fronds each with several to very many pinnules |
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(2) |
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| 2 (1) |
Fronds 1-3-palmate or dichotomously branched |
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(3) |
| + |
Fronds 1-4-pinnate |
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(7) |
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| 3 (2) |
Fronds 2- or 3-dichotomously or nearly dichotomously branched, primary branches with 1-pinnate pinnae on both sides |
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(4) |
| + |
Fronds pedately branched, with 2-6(or 8) 1-pinnate pinnae per branch |
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(5) |
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| 4 (3) |
Pinnules including indusia hairy. |
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18 A. hispidulum |
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Pinnules glabrous. |
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19 A. flabellulatum |
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| 5 (3) |
Sori 1 or 2 per pinnule; lamina ca. 15 cm; pinnules ca. 10 ?3-4 mm. |
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17 A. subpedatum |
| + |
Sori 4-6 per pinnule; pinnules ca. 20 ?6 mm |
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(6) |
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| 6 (5) |
Pinnules with upper margin divided for 1/3-1/2 of length, apex with blunt serrations, abaxially green; indusia retuse at upper margin. |
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15 A. pedatum |
| + |
Pinnules with upper margin more shallowly lobed, apex with acute triangular serrations, abaxially glaucous; indusia deeply sinuate at upper margin. |
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16 A. myriosorum |
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| 7 (2) |
Fronds 1-pinnate, lanceolate or linear-lanceolate in outline |
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(8) |
| + |
Fronds 2-4-pinnate |
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(21) |
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| 8 (7) |
Pinnules entire, stalk ?articulate at apex and pinnule easily lost when dry |
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(9) |
| + |
Pinnules ?divided, stalk not articulate and pinnule persistent when dry |
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(13) |
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| 9 (8) |
Plants small, creeping, 1.5-3 cm tall, lamina with 3-5 small orbicular pinnules; indusia orbicular, upper margin truncate, 1 per pinna. |
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2 A. mariesii |
| + |
Plants erect, above 3 cm tall, lamina usually with 5-7 or more flabellate pinnules; indusia reniform or elongated, upper margins retuse or truncate, 1 to many per pinna |
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(10) |
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| 10 (9) |
Plants soft and weak; lamina narrowly flabellate, thin in texture, stipe as slender as a hair, 1/3-1/2 as long as pinnae. |
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3 A. lianxianense |
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Plants strong; lamina broadly flabellate, stipe robust, less than 1/5 as long as lamina |
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(11) |
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| 11 (10) |
Pinnules obtriangular, indusia depressed at upper margins, scale margins denticulate. |
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4 A. gravesii |
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Pinnules orbicular-flabellate or obtriangular, indusia truncate at upper margins, scale margins entire |
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(12) |
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| 12 (11) |
Pinnules orbicular-flabellate, usually with 3 or 4 sori. |
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5 A. juxtapositum |
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Pinnules obtriangular, with 1(or 2) sori. |
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6 A. chienii |
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| 13 (8) |
Apex of frond not prolonged into whiplike structure. |
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19 A. diaphanum |
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Apex of frond usually elongated and whiplike, often forming plantlet at end |
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(14) |
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| 14 (13) |
Stipes, rachises, and both sides of lamina multicellular brown hirsute |
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(15) |
| + |
Stipes, rachises, and both surfaces of lamina glabrous or occasionally with 1 or 2 stiff hairs |
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(18) |
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| 15 (14) |
Pinnule upper margins subentire or crisped or lobed for ca. 1/3 of breadth of pinnule or with 3 or 4 short, broad lobes |
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(16) |
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Pinnule upper margins with many long lobes; widely distributed S of Chang Jiang, common |
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(17) |
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| 16 (15) |
Stipe 4-12 cm, densely hairy; lamina 1.2-2.4 cm wide; sori 2 or 3 per pinnule; Yunnan, rare. |
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9 A. sinicum |
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Stipe 10-20 cm, very sparsely hairy or glabrous; lamina 3-6 cm wide; sori 5-16 per pinnule; Taiwan, rare. |
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10 A. meishanianum |
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| 17 (15) |
Basal pair of pinnules smaller than immediately distal pinnules; abaxial surface of rachis and lamina sparsely hairy, hairs facing all directions; rhizome scale margins entire. |
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7 A. caudatum |
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Basal pair of pinnules larger than more distal pinnules; abaxial surface of rachis and lamina densely hairy, hairs appressed and facing laminal front; rhizome scale margins serrate. |
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8 A. malesianum |
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| 18 (14) |
Stipes, rachises, and stalks with membranous, brown wings. |
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11 A. soboliferum |
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Stipes, rachises, and stalks terete |
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(19) |
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| 19 (18) |
Pinnules semidimidiate, subsessile. |
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14 A. edgeworthii |
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Pinnules semilunar, orbicular-flabellate, or orbicular, with longer stalk |
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(20) |
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| 20 (19) |
Pinnules lunate, base asymmetrical, stalk ca. 10 mm. |
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12 A. philippense |
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Pinnules orbicular-flabellate or orbicular, base symmetrical, stalk 2-3 mm. |
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13 A. capillus-junonis |
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| 21 (7) |
Pinnules with sparse deep brown and appressed long needlelike setae. |
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21 A. diaphanum |
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Pinnules glabrous |
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(22) |
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| 22 (21) |
Rachises and stalks brown hispidulous |
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(23) |
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Rachises, stalks, and pinnules glabrous |
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(24) |
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| 23 (22) |
Rhizome short and erect, fronds clustered; pinnules 2 pairs per pinna; sori 4-6 per pinnule (rarely 1 or 2 on ultimate pinnules). |
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20 A. induratum |
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Rhizome long creeping, fronds spaced; pinnules 4 or 5 pairs per pinna, stiffly papery; sori 1(or 2) per pinnule. |
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24 A. davidii |
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| 24 (22) |
Pinnules with upper margin entire, bluntly toothed, or undulate-crenate |
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(25) |
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Pinnules with upper margin densely finely sharply toothed to erose-dentate |
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(29) |
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| 25 (24) |
Rhizome long creeping; upper margin of pinnules distinctly bluntly triangular serrate. |
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29 A. monochlamys |
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Rhizome shortly creeping or ascending; upper margin of pinnules entire or undulate-crenate |
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(26) |
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| 26 (25) |
Upper margin of pinnules undulate-crenate; sori mostly 1 per pinnule. |
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30 A. erythrochlamys |
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Upper margin of pinnules entire; sori 2-4 per pinnule |
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(27) |
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| 27 (26) |
Pinnules 8-14 mm wide. |
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33 A. refractum |
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Pinnules 4-7 mm wide |
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(28) |
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| 28 (27) |
Pinnules triangular, leathery. |
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31 A. roborowskii |
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Pinnules fan-shaped, herbaceous. |
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32 A. formosanum |
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| 29 (24) |
Plants to 10 cm tall; fronds 2-pinnate; indusia rectangular, truncate at upper margins; pinnules nearly as long as wide. |
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22 A. fengianum |
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Plants more than 15 cm tall; fronds usually 3-pinnate; indusia orbicular, orbicular-reniform, or oblong |
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(30) |
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| 30 (29) |
Stipe base densely brownish, multicellular setose (setae deciduous but leaving marks and rough feel). |
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23 A. bonatianum |
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Stipe base glabrous |
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(31) |
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| 31 (30) |
Pinnule 12-20 ?10-15 mm, upper margin 2-4-lobed; sori 3-10 per pinnule. |
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34 A. capillus-veneris |
| + |
Pinnule 3-11(-13) ?3-13 mm, upper margin truncate, curved, or emarginate; sori 1-3(-5) per pinnule |
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(32) |
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| 32 (31) |
Indusia orbicular or reniform, upper margins emarginate or curved |
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(33) |
| + |
Indusia elongated or orbicular-reniform, upper margins truncate or slightly curved |
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(34) |
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| 33 (32) |
Indusia orbicular, upper margins sinuate; pinnule abaxially green; veins distinctly raised. |
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25 A. venustum |
| + |
Indusia reniform, upper margins curved; pinnule abaxially glaucous; veins indistinct. |
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26 A. tibeticum |
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| 34 (32) |
Upper margins of pinnules with long and sharp serrations. |
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27 A. fimbriatum |
| + |
Upper margins of pinnules with short and obtuse serrations. |
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28 A. breviserratum |
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List of lower taxa
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