Pellaea truncata
Pellaea atropurpurea
cliff brake, spiny cliff-brake
pelléade à stipe pourpre, purple cliff-brake, purple-stem cliff-brake
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 (or tan), linear-subulate, 0.1–0.3 mm wide, thin, margins entire to denticulate.
somewhat dimorphic, sterile leaves shorter and less divided than fertile leaves, clustered on stems, 8–40 cm;
croziers sparsely villous.
somewhat dimorphic, sterile leaves shorter and less divided than fertile leaves, clustered on stems, 5–50 cm;
croziers villous.
dark brown, lustrous, flattened or slightly grooved adaxially, without prominent articulation lines.
reddish purple to nearly black, lustrous, rounded adaxially, without prominent articulation lines.
ovate-deltate, usually 2-pinnate proximally, 4–18 cm wide;
rachis brown throughout, straight, shallowly grooved adaxially, usually glabrous.
elongate-deltate, usually 2-pinnate proximally, 2–18 cm wide;
rachis reddish purple throughout, straight, rounded adaxially, densely pubescent adaxially with short, curly, appressed hairs.
narrowly oblong, 4–10 mm, leathery, glabrous;
margins recurved on fertile segments, usually covering less than 1/2 abaxial surface, borders whitish, nearly entire;
apex mucronate.
linear-oblong, 10–75 mm, leathery, sparsely villous abaxially near midrib;
margins weakly recurved to plane on fertile segments, usually covering less than 1/2 abaxial surface, borders whitish, crenulate;
apex obtuse to slightly mucronate.
perpendicular to rachis to slightly ascending, not decurrent on rachis, usually with 9–25 ultimate segments;
costae straight, 20–70 mm, much longer than fertile ultimate segments.
perpendicular to rachis or ascending, not decurrent on rachis, usually with 3–15 ultimate segments;
costae straight, 10–100 mm, often longer than ultimate segments.
of ultimate segments obscure.
of ultimate segments obscure.
long-stalked, containing 64 spores, intermixed with abundant farina-producing glands.
long-stalked, containing 32 spores, not intermixed with farina-producing glands.
= 2n = 87, apogamous.
= 58.
Pellaea truncata
Pellaea atropurpurea
Most manuals refer to Pellaea truncata as P. longimucronata, a name shown to be invalid by A. Cronquist et al. (1972+, vol. 1). Populations located near the range of P. mucronata in the Mojave Desert are often difficult to identify because of the subtlety of the characters involved and an apparent tendency to produce sterile (and possibly fertile) hybrids. Morphologically intermediate hybrids between P. truncata and P. wrightiana are common in regions where the ranges of the two species overlap, but these are easily identified by their malformed spores.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Contrary to D. B. Lellinger's (1985) hypothesis, isozyme data indicate that neither Pellaea glabella nor P. ternifolia was involved in the origin of this apogamous triploid. Instead, it appears that P. atropurpurea is an autopolyploid derivative of a single diploid taxon that has not yet been located. A thorough survey of spore number per sporangium in this species should be undertaken to determine whether the diploid progenitor is still extant. Collections from western Canada identified as P. atropurpurea actually represent P. gastonyi, an apogamous tetraploid produced by hybridization between P. atropurpurea and diploid populations of P. glabella. Pellaea atropurpurea has also hybridized with P. wrightiana; the hybrid is a rare apogamous pentaploid known only from western Oklahoma. Pellaea lyngholmii is the apogamous tetraploid hybrid between P. atropurpurea and P. truncata. Pellaea atropurpurea is distinguished from all these hybrids by having rachises that are densely pubescent adaxially, larger ultimate segments, and spores averaging less than 62 µm in diameter.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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