Nephrolepis undulata (Afzel. ex Sw.) J.Sm.
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Authority
Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
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Family
Nephrolepidaceae
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Scientific Name
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Description
Species Description - Rhizomes erect, almost non-existent, stoloniferous, with oval tubers; rhizome scales concolorous, linear, orange to pale brown, 1.5–3 x 0.5–1 mm; stipes 4–11 cm long, 1/4–1/6 the frond length, stramineous, glabrous or with scattered linear scales, grooved; blades thinly herbaceous (veins distinct), linear-elliptic, 22–50 x 3.5–7 cm; rachises stramineous, glabrous except for sparse concolorous, pale brown, linear to fimbriate hair-like scales 1–1.5 mm long, these mostly at pinna bases; pinnae 15–30(–38) pairs, sessile, narrowly deltate, 2–4.5 x 0.8–1.2 cm at bases, apices acuminate, bases unequally lobed with basiscopic lobe small, rounded to subcordate, and rarely overlapping rachis adaxially, acroscopic lobe much larger and overlapping rachis abaxially, margins crenate, especially on the fertile fronds, on sterile ones only slightly so; indument on both blade surfaces absent; hydathodes rarely lime-dotted on adaxial blade surfaces; indusia pale brown, lunate, 1.5–2 mm in greatest dimension, attached along broad, shallow sinuses, mostly opening toward pinna apices; 2n=ca. 90, probably erroneous (Nay), 82 (Afr).
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Discussion
Aspidium undulatum Afzel. ex Sw., J. Bot. (Schrader) 1800(2): 31. 1801. Type. Sierra Leone. Afzelius s.n. (BM!). Nephrolepis occidentalis Kunze, Linnaea 18: 343. 1844. Type. Mexico. Leibold 27 [127] (holotype LZ, destroyed; presumed isotype B!). For a discussion of typification, see Pichi Sermolli (1968). Nephrolepis intermedia Fe´e, Me´m. Foug. 9: 32. 1857. Type. Mexico. [Veracruz:] Orizaba, Schaffner 447 (isotype K!).
Nephrolepis undulata is the most widespread member of its genus in Mexico, and is distinct in its weakly developed rhizomes, presence of tubers below ground, entire rhizome scales, thin-textured pinnae with distinct veins, small number of pinnae (usually fewer than 35 pairs), pinnae tapering from bases to acute apices, and large lunate indusia 1.5–2 mm wide. The presence of perennating, underground tubers enables this species to survive burning and helps perpetuate an annual flush of growth with the advent of the rainy season; in times of drought, the plants disappear aboveground. This species is usually treated under the name N. occidentalis (e.g., by Smith, 1981; Mickel & Beitel, 1988), but we find no essential differences between the paleotropical and neotropical specimens of this very widespread species. R. Tryon and Stolze (1993: 53) believed that there exists intergradation between N. undulata (as occidentalis) and N. pectinata in South America, but we see no evidence of such intermediates in Mexico and find the two taxa amply distinct throughout their ranges. Breedlove 28698 (DS), from Chiapas, is an aberrant (dissected) form of the species.