Monographs Details: Adiantum capillus-veneris L.
Authority: Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Description:Species Description - Rhizomes short-creeping, 2–4 mm diam.; rhizome scales castaneous, concolorous, ca. 2–2.5 x 0.1–0.3 mm, margins entire; fronds clumped, 15–45(–70) cm long, arching or pendent; stipes castaneous to atropurpureous, lustrous, 7–35 cm x 0.5–1.5 mm,ca. 1/2 the frond length, glabrous except at bases; blades ovate to ovate-lanceolate, 2–3 times pinnate, ca. 5–22 cm wide, tapering to apices; rachises castaneous, glabrous; pinnae 3–7 compound pairs, alternate, stalked; pinnulets obovate, flabellate, or rhombic, 5–30 mm long, cuneate at bases, margins often deeply lobed or incised distally, 2 or more clefts per pinnulet, sterile margins strongly denticulate, color passing into base of pinnulets, nonarticulate; veins free, forking, ending in teeth; indument absent on both sides of blades, laminae not glaucous; idioblasts absent; sori 2–6 per pinnulet, confined to distal margins; indusia 1–5 mm long; oblong to arcuate, glabrous; 2n=60 (OldWorld), 120 (USA).

Discussion:Lectotype (chosen by Pichi Sermolli, Webbia 12: 678, 1957). France. Magnol s.n. (LINN 1252.9, microfiche UC). Adiantum schaffneri E. Fourn., Bull. Soc. Bot. France 27: 328. 1880. Type. Mexico. San Luis Potosi´: “in montibus circa San Luis de Potosi´,” Schaffner 64 (P!, frag. NY!, photos BM!, BR, US!). Adiantum capillus-veneris L. var. protrusum Fernald, Rhodora 52: 203. 1950. Type. U.S.A. Georgia: Clay Co., Samochechobee Creek, Harper 1791 (GH). Adiantum modestum Underw., Bull. Torrey Bot. Club 28: 46. 1901. Adiantum capillus-veneris L. var. modestum (Underw.) Fernald, Rhodora 52: 206. 1901. Type. U.S.A. New Mexico: North Spring River, Roswell, Earle 261 (GH; isotype GH). Unverified, Doubtful, or Mistaken Reports. Sin (reported by Vega A. et al., 1989, but not verified). Of the Adiantum species with blades gradually tapering distally, only a few have the veins ending in teeth. Adiantum capillus-veneris is the most conspicuous in this respect, with its strongly denticulate margins. Adiantum andicola is sparingly and shortly toothed and differs in its blackish rhizome scales. There is significant variation within A. capillus-veneris, even within Mexico, in such characters as depth of lobing or incision of the pinnulets (both fertile and sterile), size of segments, length-to-width ratio of pinnulets, size and degree of dissection of blades, and extent of creeping of the rhizomes. Fernald (1950) recognized two intergrading varieties of this widespread species in the United States and Mexico, while restricting the type variety to Europe. Variety modestum was said by him to differ chiefly in its firmer texture, small, barely notched fertile pinnulets and Cordilleran distribution in the United States.We are unable to apply the characters discussed by Fernald to distinguish varieties in the New World, or even to distinguish the European plants from those of the United States and Mexico. In general, sterile and/or juvenile plants or fronds, in many parts of the species range, often have more deeply cleft pinnulets than fertile plants or fronds.

Distribution and ecology: Terrestrial on wooded stream banks or epipetric on limestone in seepage areas; ravines with Taxodium and Ficus, tropical deciduous forests, matorral, lower montane rain forests, evergreen rain forests; 150–2450 m. USA; Mexico; Guat, Bel, Hond; Berm, Bah, Gr & L Ant; Ven, Trin, Peru; Eur, Africa, Asia, Pac Is. Selected Specimens Examined. Ags (Siqueiros D. 4295, IEB). BCN (Wiggins 10030, DS, UC). BCS (Carter & Sharsmith 4240, NY, UC, US. Cedros (Anthony 114, DS, MO, NY, UC, US). Chih (Johnston et al. 11375, CAS). Chis (Matuda 2423, MEXU, NY, US). Coah (Palmer 71, MO, UC, US). DF (Schaffner 120, in 1875, NY). Dgo (Palmer 77, MO, UC). Gro (Lorea 1141, ENCB, FCME). Gto (McVaugh 14834, NY). Hgo (Ortega 86, IEB). Jal (Jones 497b, US). Méx (Ventura 422, ENCB, NY). Mich (Hinton 15895, NY, UC). Mor (Hinton 17079, ENCB, NY). Nay (Téllez 9164, IEB p.p.). NL (Hinton 17508, ENCB, MEXU). Oax (Mickel 6301, NY, UC). Pue (Orcutt 2098, DS). Qro (Fernández N. 3773, ENCB, IEB). SLP (Copeland herb. 112, UC, US). Son (Hartman 292, UC, US). Tam (Palmer 189, MO, NY, UC, US). Tlax (Langman 2584, US). Ver (Vázquez et al. 379, NY). Zac (Lloyd 13, UC, US).