Belongs within: Pteridaceae.
Adiantum, the maidenhair ferns, is a cosmopolitan genus of ferns with relatively delicate fronds.
Characters (Hickman 1993): Rhizome short-creeping, scales variously colored. Leaf up to about 1 m; petiole cylindric, generally dark reddish brown to blackish, shiny, more or less scaly at base; blade 2–3-pinnate or more or less palmate-pinnate (first division more or less palmate, subsequent ones pinnate), segments stalked, fan-shaped or oblong, generally lobed, toothed, or both; axes, blades lacking colored exudate. Sporangia borne along veins on and covered by highly modified, recurved part of segment margin, appearing to run together at maturity; false indusia more or less semi-circular to linear; spores generally smooth, tan.
<==Adiantum Linnaeus 1753A61
|--+--A. pedatum Linnaeus 1753SP09, I88
| `--+--A. capillus-veneris Linnaeus 1753SP09, B06
| `--A. malesianumSP09
`--+--A. tenerum Sw. 1783-1787SP09, B06
`--+--A. peruvianumSP09
`--A. tetraphyllumSP09
Adiantum incertae sedis:
A. aethiopicum Linnaeus 1753 [incl. A. assimile Swartz 1806, A. trigonum Labill. 1806]A61
A. aleuticum (see below for synonymy)H93
A. capillus-junorisI88
A. caudatum Linnaeus 1771I88
A. chilienseBS-V28
A. concinnumL54
A. cunninghamii Hook. 1858 (see below for synonymy)A61
A. diaphanum Blume 1828 (see below for synonymy)A61
|--A. d. var. diaphanumB78
`--A. ‘affine’ var. intermediumB78
A. edgeworthii Hooker 1851 (see below for synonymy)I88
A. flabellulatum Linnaeus 1753I88
A. formosum Br. 1810A61
A. fragileJ87
A. fulvum Raoul 1846 [incl. A. viridescens Colenso 1895]A61
A. hispidulum Swartz 1801A61 [incl. A. birkenheadii Moore 1886C06, A. pubescens Schkuhr 1809A61]
A. incisum Forskål 1775 [incl. A. vestitum Wall. 1829 (n. n.)]B06
A. jordaniiH93
A. parishiiB66
A. philippines Linnaeus 1753 [incl. A. lunulatum Burmann 1768]B06
A. pyramidaleJ87
A. silvaticumH90
A. soboliferumI88
A. × tracyi [A. aleuticum × A. jordanii]H93
A. venustum Don 1825I88
Nomen nudum: Adiantum deperditum Squinabol 1889S89
Adiantum aleuticum [=A. pedatum var. aleuticum; incl. A. boreale, A. aleuticum ssp. calderi, A. aleuticum var. subpumilum]H93
Adiantum cunninghamii Hook. 1858 [incl. A. affine var. chathamicum Field 1890 (n. n.), A. formosum Rich. 1832 non Br. 1810, A. affine var. heterophyllum Colenso 1888, A. pullum Colenso 1873]A61
Adiantum diaphanum Blume 1828 [incl. A. affine Hook. 1858 (preoc.), A. polymorphum Col. 1888, A. diaphanum var. polymorphum (Col.) Cheeseman 1906, A. setulosum Smith 1846, A. tuberosum Col. 1888]A61
Adiantum edgeworthii Hooker 1851 [=A. caudatum var. edgeworthii (Hooker) Bedd. 1883; incl. A. caudatum var. rhizophorum Wallich ex Hooker 1851]I88
*Type species of generic name indicated
References
[A61] Allan, H. H. 1961. Flora of New Zealand vol. 1. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. R. E. Owen, Government Printer: Wellington (New Zealand).
[B66] Beavan, R. C. 1866. Extracts from a letter addressed to the Secretary relating his trip to Zwagaben, and discovery of Nemorhaedus sumatrensis. Proceedings of the Zoological Society of London 1866: 2–4.
[B78] Bentham, G. 1878. Flora Australiensis: A description of the plants of the Australian Territory vol. 7. Roxburghiaceae to Filices. L. Reeve & Co.: London.
[B06] Biswas, A. 2006. Pteridophytes of Indian Botanic Garden, Howrah. Bulletin of the Botanical Survey of India 48: 175–188.
[BS-V28] Bory de Saint-Vincent, J. B. 1828. Voyage Autour du Monde, Exécuté par Ordre du Roi, Sur la Corvette de Sa Majesté, La Coquille, pendant les années 1822, 1823, 1824 et 1825. Botanique. Cryptogamie. Arthus Bertrand: Paris.
[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.
[H90] Harden, G. J. (ed.) 1990. Flora of New South Wales vol. 1. New South Wales University Press.
[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).
[I88] Iwatsuki, K. 1988. An enumeration of the pteridophytes of Nepal. In: Ohba, H., & S. B. Malla (eds) The Himalayan Plants vol. 1. The University Museum, University of Tokyo, Bulletin 31: 231–339.
[J87] Judd, W. S. 1987. Floristic study of Morne La Visite and Pic Macaya National Parks, Haiti. Bulletin of the Florida State Museum—Biological Sciences 32 (1): 1–136.
[L54] Lötschert, W. 1954. Beitrag zur Pteridophyten-Flora von Mittel-Amerika. Senckenbergiana Biologica 35 (1-2): 109–119.
[SP09] Schuettpelz, E., & K. M. Pryer. 2009. Evidence for a Cenozoic radiation of ferns in an angiosperm-dominated canopy. Proceedings of the National Academy of Sciences of the USA 106 (27): 11200–11205.
[S89] Squinabol, S. 1889. Res Ligusticae. VII.—Cenno preliminare sulla flora fossile di Santa Giustina. Annali del Museo Civico di Storia Naturale di Genova, Serie 2a, 7: 73–76.