Adiantum trapeziforme L.

  • 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 trapeziforme L.

  • Description

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    Species Description - Rhizomes short- to long-creeping, 3–5 mm diam.; rhizome scales bicolorous, light brown at bases to lustrous dark brown at tips, linear-lanceolate, denticulate, 2–3 x 0.1–0.3 mm; fronds distant, (40–)60–100 cm long, arching; stipes atropurpureous to blackish, lustrous, 35–60 cm x 4–6 mm, nearly 1/2 the frond length, glabrous except at bases, with minute tubercles; blades broadly ovate, 3–4-pinnate proximally, 2-pinnate distally, each blade with a conform, 1-pinnate terminal pinna; rachises atropurpureous, glabrous; pinnae 3–4 compound pairs, the proximal pair the longest, 25–35 x ca. 15 cm; pinnulets mostly trapeziform, inequilateral, (20–)35–50 x 10–20 cm, acute to acuminate at tips, sterile margins incised-lobate, fertile margins only shallowly so, stalked 1–5 mm, articulate, stalk color ending abruptly at pinnulet bases, articulate; veins free, forking, ending in teeth at the margins; indument absent on both blade surfaces, blades sometimes glaucous abaxially; idioblasts absent; sori 10–15 along acroscopic margins of pinnules, 1–2 per lobe, also 3–5 along distal margins; indusia 1–3 mm long; oblong, glabrous; 2n = 60, 90 (cult).

  • Discussion

    Lectotype (chosen by Lellinger, Proc. Biol. Soc. Wash. 89: 704. 1977). Sloane, Voy. Jamaica 1: t. 59. 1707.

    Adiantum trapeziforme L. var. oblongatum T. Moore, Index Fil. 40. 1857. Syntypes. Mexico. Veracruz: Cordillera de Veracruz, Galeotti 6338 (K); Guatemala, Skinner s.n. (K); Cuba. Poeppig s.n. (K). Based on the description of A. trapeziforme ?, an unnamed variant, in Hook., Sp. Fil. 2: 33. 1851. Adiantum trapeziforme L. var. plumieri T. Moore, Index Fil. 40. 1857. Syntypes. Mexico. Veracruz: near Veracruz, Linden 70 (K); Plumier, Traite´ Foug. Ame´r., pl. 95. 1705. Based on the description of A. trapeziforme ß, an unnamed variant, in Hook., Sp. Fil. 2: 33. 1851. Unverified, Doubtful, or Mistaken Reports. Tab (reported by Magan˜a, 1992, but not verified). Among the tripinnate species with a conform terminal pinna, A. trapeziforme is distinctive in its glabrous stipes, rachises and pinnulets, articulate pinnulets, and lack of epidermal idioblasts. South American material has been ascribed to this species; some of these specimens, especially from Peru, Bolivia, and Brazil, have been named A. mathewsianum Hook., which is certainly very closely related to A. trapeziforme. Additionally, true A. trapeziforme may be naturalized in South America, as it seems to be in Paraguay and in areas of Asia and the Pacific. Further study is needed.