Adiantum tenerum Sw.

  • Authority

    Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.

  • Family

    Pteridaceae

  • Scientific Name

    Adiantum tenerum Sw.

  • Description

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    Species Description - Rhizomes short-creeping, 5–10 mm diam.; rhizome scales ferrugineous, becoming dark brown in center portion (and so somewhat bicolorous), lustrous, 2–3 x 0.8–1 mm, margins ciliate-fimbriate; fronds clumped, 25–110 cm long, laxly arching; stipes atropurpureous to blackish, lustrous, 10–55 cm x 1.5–3 (–4) mm, 1/3–1/2 the frond length, glabrous or with rare minute tubercles; blades ovate-deltate, 3–5-pinnate proximally, 18–15 x (15–)20–40 cm wide; rachises atropurpureous, glabrous, somewhat flexuous toward tips; pinnae 5–9 compound pairs, alternate, stalked to 4 cm, gradually tapering distally; pinnulets trapeziform to rhombic, or flabellate at blade and pinna apices, fertile pinnulets 1–2 cm long and wide, cuneate at bases, denticulate cleft or lobed distally, sterile pinnulets somewhat larger than the fertile ones, stalked 2–4 mm, stalk color stopping abruptly at bulge at pinnulet bases, articulate; veins free, forking, ending in marginal teeth; indument absent on both blade surfaces, blades sometimes glaucous abaxially; idioblasts absent; sori to ca. 12 per pinnulet, confined to distal margins, with slight yellow farina among sporangia; indusia 1–3 mm long, reniform to oblong, glabrous; 2n=60 (USA, Ver, CR, Jam).

  • Discussion

    Type. Jamaica. Swartz s.n. (S).

    Adiantum trapezoides Fe´e, Me´m. Foug. 5: 117. 1852. Type. Mexico. Veracruz: Puente Nacional, Galeotti 6317 (P!; isotype RB). ?Adiantum extensum Fe´e, Me´m. Foug. 8: 72. 1857. Syntypes. Mexico. Veracruz: near Orizaba and Huatusco, Schaffner 40 (P?), 41 (P?, RB). Unverified, Doubtful, or Mistaken Reports. Tres Marias (Nelson 4281, US, cited by Lenz, 1995, as A. tenerum, and Ferris 5704, DS, and Mason 1822, CAS, cited by Lenz as A. trapezoides, but none verified, all three probably misidentifications). Adiantum tenerum most closely resembles A. amplum, from which it differs by having smaller, bicolorous rhizome scales, serrulate sterile pinnulets, and the generally more flabellate pinnulets. They also differ in general distribution, A. tenerum being an Atlantic slope species and A. amplum a Pacific slope species. Adiantum tenerum is very common in Veracruz and Chiapas, but less common elsewhere. A specimen cited by Di´az-Barriga and Palacios-Rios (1992) from Michoaca´n (Hinton 15956, ENCB) is A. amplum.

  • Distribution

    Terrestrial in lowland forests of the Atlantic lowlands, woods along streams, tropical forests, evergreen rain forests, coffee plantations, calcareous cliffs; 50-1350 m. USA (Fla); Mexico; Guat, Bel, Hond, Nic, CR; Bah, Gr & L Ant; Ven, Trin.

    Mexico North America| Trinidad and Tobago South America| Venezuela South America| West Indies| Bahamas South America| Costa Rica South America| Nicaragua Central America| Honduras Central America| Belize Central America| Guatemala Central America|