Classification
 Nomenclature
Scientific Name:
Adiantum capillus-veneris L., Sp. Pl. 1095 (1753)
Synonymy:
Lectotype (selected by Pichi Sermolli 1957): [Habitat in Europa australis – southern Europe], Magnol, LINN 1252.9 (!online; see Jarvis 2007).
  • = Adiantum affine Willd., Sp. Pl. 5(1), 448 (1810)
Holotype: [Nova Zeelandia], no locality or collector, B-W 20093-01 0 (!online)
Etymology:
From the Latin capillus (hair), veneris (of Venus), giving rise to the popular and widespread name of maidenhair.
Vernacular Name(s):
European maidenhair; Venus-hair fern
 Description

Rhizomes short-creeping, up to 60 mm long (in herbarium specimens), 2–3 mm diameter, with stipes closely inserted; bearing scales; stolons and tubers absent. Rhizome scales narrowly ovate, 2–3.5 mm long, 0.2–0.4 mm wide, orange-brown, concolorous. Fronds 40–435 mm long. Stipes 20–210 mm long, dark brown, polished, glabrous except for a few scattered scales proximally. Rachises dark brown, sulcate, polished, glabrous. Laminae usually 2-pinnate, rarely 1-pinnate in very small fronds or 3-pinnate in large fronds, ovate, 20–270 mm long, 14–165 mm wide, mid-green on both surfaces, herbaceous, glabrous. 1–8 pairs of divided  primary pinnae below pinnate apex, widely spaced especially proximally, ovate; the longest at or near the base, 8–115 mm long, 7–50 mm wide, apices obtuse, bases stalked, usually divided into secondary pinnae except in very small fronds. Longest secondary pinnae flabellate, 5–36 mm long, 5–16 mm wide, apices obtuse or rounded, margins deeply incised in largest fronds, or rarely divided into 1–3 tertiary pinnae, bases stalked, with stalks attached centrally. Reflexed lamina flaps oblong, extending laterally up to 5 mm, glabrous.

 Recognition

Adiantum capillus-veneris is distinguished by its usually 2-pinnate fronds, flabellate ultimate segments with the stalks attached centrally, glabrous rachises and laminae, oblong and glabrous “indusia”, and green abaxial lamina surface. The oblong or elongated reflexed lamina flaps distinguish this species from all other species of Adiantum in New Zealand.

 Distribution

North Island: Auckland, Southern North Island.

South Island: Western Nelson, Canterbury.

Altitudinal range: 0–140 m.

Adiantum capillus-veneris has been recorded from urban sites in Auckland, Waihi, Hamilton, Wellington, Westport and Christchurch.

Occurs naturally in tropical and temperate areas of North and South America, Europe, Asia, Africa, Australia and Hawai‘i. Its status in other Pacific islands is uncertain due to confusion with A. tenerum Sw.

 Habitat

Adiantum capillus-veneris grows most commonly on brick or concrete walls in urban areas, or occasionally on road or trackside banks, or on scoria.

 Biostatus
Exotic
 First Record

Brownsey (1981). Voucher CHR 366041, 1978.

 Notes

Tindale (1960) treated Willdenow’s Adiantum affine as a new species (although the illegitimate A. trapeziforme G.Forst. was cited), with a holotype from Willdenow’s herbarium (B-W 20093 -01 0). As pointed out by Tindale (1960) and Nicolson & Fosberg (2003), the holotype of A. affine is a specimen of A. capillus-veneris. The specimen is said to be from New Zealand, which is also the only locality given in Willdenow’s protologue. However, it is extremely unlikely that A. capillus-veneris was present in New Zealand at the time of Cook’s second voyage, and hence it must be concluded that the provenance of Willdenow’s specimen was somehow confused. The name A. affine was widely used in earlier New Zealand Floras for the plant now known as A. cunninghamii.

 Bibliography
Brownlie, G. 1961: Additional chromosome numbers – New Zealand ferns. Transactions of the Royal Society of New Zealand. Botany 1: 1–4. [as Adiantum affine Willd.]
Brownsey, P.J. 1981: Checklist of pteridophytes naturalised in New Zealand. New Zealand Journal of Botany 19: 9–11.
Brownsey, P.J.; Perrie, L.R. 2021: Pteridaceae. In: Breitwieser, I. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 30. Manaaki Whenua Press, Lincoln.
Jarvis, C.E. 2007: Order out of chaos: Linnaean plant names and their types. Linnean Society of London in association with the Natural History Museum.
Linnaeus, C. 1753: Species Plantarum. Impensis Laurentii Salvii, Stockholm.
Nicolson, D.H.; Fosberg, F.R. 2003: The Forsters and the Botany of the Second Cook Expedition (1772–1775). Regnum Vegetabile 139: 1–760.
Pichi Sermolli, R.E.G. 1957: Adumbratio florae Aethiopicae. 5. Parkeriaceae, Adiantaceae, Vittariaceae. Webbia 12: 645–703.
Tindale, M.D. 1960: Notes on Pteridophytes from Australasia and New Caledonia I. American Fern Journal 50: 117–124.
Willdenow, C.L. 1810: Species Plantarum. Vol. 5 (1). G.C. Nauk, Berlin.