Pellaea ternifolia |
Pellaea gastonyi |
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trans-Pecos cliffbrake |
Gastony's cliff-brake, Gastony's cliffbrake fern |
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Stems | compact, ascending, stout, 5–10 mm diam.; scales bicolored, linear-subulate, 0.1–0.3 mm wide, centers black, thick, margins brown, thin, erose-dentate. |
compact, ascending, stout, 5–10 mm diam.; scales uniformly reddish brown, linear-subulate, 0.1–0.3 mm wide, thin, margins entire to denticulate. |
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Leaves | monomorphic, clustered on stem, 10–50 cm; croziers sparsely to densely villous. |
somewhat dimorphic, sterile leaves shorter than fertile leaves, clustered on stem, 8–25 cm; croziers villous. |
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Petiole | black or dark purple, lustrous, rounded or slightly flattened adaxially, without prominent articulation lines. |
reddish purple to dark brown, lustrous, rounded adaxially, without prominent articulation lines. |
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Blade | linear to ovate, deeply pinnate-pinnatifid proximally, 2.5–8 cm wide; rachis black or purple throughout, straight, often flattened adaxially, glabrous or villous. |
elongate-deltate to lanceolate, 2-pinnate proximally, 3–6 cm wide; rachis purple or brown throughout, straight, rounded adaxially, sparsely villous with long, divergent hairs. |
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Ultimate segments | linear-oblong, 10–40 mm, leathery, glabrous to sparsely villous abaxially on midrib; margins recurved on fertile segments, rarely covering more than 1/2 abaxial surface, borders whitish, entire; apex mucronate. |
oblong-lanceolate, 7–30 mm, leathery, sparsely villous abaxially near midrib; margins usually recurved on fertile segments, covering less than 1/2 abaxial surface, borders whitish, crenulate; apex obtuse to slightly mucronate. |
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Pinnae | perpendicular to rachis or slightly ascending, not decurrent on rachis, ternate at base of leaf; costae absent. |
ascending or perpendicular to rachis, not decurrent on rachis or obscurely so, usually with 3–7 ultimate segments; costae straight, 2–30 mm, usually shorter than ultimate segments. |
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Veins | of ultimate segments obscure. |
of ultimate segments obscure. |
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Sporangia | long-stalked, containing 64 spores, not intermixed with farina-producing glands. |
long-stalked, containing 32 spores, not intermixed with farina-producing glands. |
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Pellaea ternifolia |
Pellaea gastonyi |
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Phenology | Sporulating summer–fall. | |||||||||
Habitat | Calcareous cliffs and ledges, usually on limestone | |||||||||
Elevation | 100–1500 m (300–4900 ft) | |||||||||
Distribution |
AZ; TX; Mexico; Central America; South America; Pacific Islands in Hawaii
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MO; SD; WY; AB; BC; SK |
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Discussion | Subspecies 3 (3 in the flora). Pellaea ternifolia is represented in the flora by three morphologically and chromosomally distinct taxa. These discrete genetic entities also show a tendency toward geographic isolation and are treated here as subspecies. Diploid populations referred to P. ternifolia subsp. ternifolia are scattered from Texas through Mexico to South America. The pubescent tetraploid (P. ternifolia subsp. villosa) follows the Sierra Madre Oriental from Puebla, Mexico, north to Texas; the glabrous tetraploid (P. ternifolia subsp. arizonica) occurs in Arizona, Texas, and northern Mexico. Isozyme and chromosome studies suggest that both tetraploids are segmental allopolyploids produced by hybridization between subsp. ternifolia and other (as yet unidentified) diploid elements within P. ternifolia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Pellaea gastonyi is an apogamous tetraploid that has originated through repeated hybridization between P. atropurpurea and P. glabella. Isozyme studies (G. J. Gastony 1988) indicate that P. glabella subsp. missouriensis was the diploid parent of plants found in Missouri, whereas diploid P. glabella subsp. occidentalis was involved in the origin of P. gastonyi populations occurring in western North America. Pellaea gastonyi is most often confused with P. atropurpurea, from which it differs in having sparsely villous rachises, smaller ultimate segments, and spores averaging more than 62 µm in diameter. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 2, p. 180. | FNA vol. 2. | ||||||||
Parent taxa | Pteridaceae > Pellaea | Pteridaceae > Pellaea | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | Pteris ternifolia | |||||||||
Name authority | (Cavanilles) Link: Fil. Spec. 59. (1841) | Windham: Contr. Univ. Michigan Herb. 19: 36. (1993) | ||||||||
Web links |