Adiantum aleuticum (Rupr.) C.A.Paris

  • 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 aleuticum (Rupr.) C.A.Paris

  • Description

    Species Description - Rhizomes short-creeping or suberect, to 5 mm diam.; rhizome scales castaneous, concolorous, 3–5 x 0.5–1 mm, margins entire; fronds densely clustered, mostly 30–60 cm long, laxly arching or pendent; stipes castaneous, lustrous, to 30 x 1–2 mm, ca. 1/2 the frond length, glabrous; blades fan-shaped or appearing palmate, actually imparipedate, mostly ca. 15–25 x 15–25 cm; rachises glabrous, sometimes glaucous; pinnae 2 lateral pairs plus a 1-pinnate terminal pinna, lateral pinnae repeatedly and unequally branching basiscopically, forked 2–4 times, to ca. 20 cm long; pinnulets oblong, tapered at tips, occasionally flabellate, basiscopic margins straight to oblique, generally ca. 2.5–4 times as long as broad, stalks to 3 mm, dark color passing into pinnulet bases or not, non-articulate; veins free, forking, ending in minute teeth in sterile pinnulets; indument absent on both surfaces; idioblasts absent; sori 6–10 per pinnulet, confined to acroscopic margins; indusia 2–3(–6) mm long, oblong to lunate, glabrous; 2n x 58 (Canada, USA).

  • Discussion

    Adiantum pedatum L. var. aleuticum Rupr., Distr. Crypt. Vasc. Ross. 49. 1845. Adiantum pedatum L. subsp. aleuticum (Rupr.) Calder & Roy Taylor, Canad. J. Bot. 43: 1388. 1965. Type. U.S.A. Alaska: Aleutian Islands, Unalaska, Chamisso s.n. (HAL?, LE?). This species is subtly different from A. pedatum L., from eastern United States and southeastern Canada. Adiantum aleuticum differs by ultimate divisions (pinnulets) with length usually more than 3.2 times the width (vs. less than 3.2 times the width in A. pedatum), apices with sharply denticulate, angular lobes (vs. apices with rounded, crenulate lobes), and lobes separated by deep sinuses 0.6-4 mm (vs. 0.1-2 mm). Traditionally, the western North America A. aleuticum has been treated as an infraspecific variant of A. pedatum, but recent biosystematic and electrophoretic work has pointed out the differences among this and several closely related north temperate species (Paris & Windham, 1988). See A. patens, the most similar Mexican species, for differences between that and A. aleuticum. Vega A. et al. (1989) reported A. pedatum for Sinaloa; we have not seen the specimen on which this is based, and none was cited, but it is possible that this refers to A. leuticum, which would be a range extension for Mexico.

  • Distribution

    In spray in recessed area beneath waterfall; 2100 m. Canada, USA; Mexico.

    Mexico North America| Canada North America| United States of America North America|