Blechnum polypodioides Raddi

Authority

Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.

Family

Blechnaceae

Scientific Name

Blechnum polypodioides Raddi

Description

Species Description - Rhizome erect or ascending, stoloniferous; rhizome scales 3-5(-9) mm long, 0.8-1 mm wide, bicolorous, central portion or apex shiny red-brown, outer or basal part pale brown, lanceolate, margin entire; fronds clumped; stipe (4-)7-9(-15) cm long, ½-1/3 the frond length, stramineous, papillate, with scattered pale brown scales 2-3 mm long; blade 14-30(-35) cm long, (3-) 4-6(-9) cm wide, pinnatisect, 18-35 pinna pairs, linear, basal pinnae distant and irregularly triangular, apex pinnatifid; rachis stramineous, with rare scales 0.8-1.3 mm long, 0.1-0.3 mm wide, otherwise either glabrous or with dense, 0.3-0.5 mm long, sticky, catenate hairs; largest pinnae 1 -5-3(-5) cm long, 6-8 mm wide at base, 3-4 (-6) mm wide in middle, linear-oblong, straight to somewhat falcate, adnate, auriculate, basal pinnae partially adnate, often deflexed, lower surface glabrous to hairy with scattered catenate hairs (0.1-0.3 mm), upper surface glabrous to hairy with scattered catenate hairs, midvein ungrooved; veins simple to once-forked, enlarged vein endings visible adaxially; pinna margin minutely toothed with intramarginal row of ser-rulations; sori 2/3 or more of pinna length, 0.5 mm wide; indusia erose.

Discussion

Type. Brazil. Corcovado, Raddi s.n. Fig. 124D. Asplenium blechnoides Lagasca ex Swartz, Syn. fil. 76. 1806. Blechnum unilaterale Swartz, Berlin. Mag. 4: 79, t. 3, f. 1. 1810, nom. superfl. illegit. Blechnum blechnoides (Lagasca ex Swartz) Christensen, Index filie. 151. 1905, nom. illeg., non Keys., 1873. Type. Peru. Née (presumably S). Blechnum pohlianum Presl, Tent, pterid. 103, t. 11, f. 11. 1836. Type. Brazil. Pohl (frag. NY!). Blechnum scabrum Liebmann, Mexic. bregn. 236 (seors. 84). 1849. Syntypes. Mexico. Oaxaca: [Choapan], Dist. Chinantla, 4000' [1220 m], Liebmann [Pl. Mex. 2305, FI. Mex. 271, 272 (C!)]. Lectotype (chosen by A. R. Smith, 1981: 60): FI. Mex. 272 (C!). Blechnum angustifrons Fée, Mém. foug. 7: 25, t. 9, f. 2. 1857. Syntypes. Mexico. [Oaxaca: Dist. Ixtlán], Llano Verde, 2500 m, Galeotti 6383 (P?; isotypes BM, BR). [Fée, in error, cited Galeotti 6284 and 6440 as type numbers (corrected in Mém. foug. 9: 4. 1857), but these specimens are B. glandulosum (q.v.).] Blechnumpolypodioides is distinguished among the monomorphic taxa by its narrow (3-9 cm wide) blade which gradually tapers both to a strictly pinnatifid apex and highly reduced basal pinnae, adnate pinnae of which only the basal few irregularly triangular pinna pairs are distant, and short stipe (7-9 cm long), which is about 1/3-¼the frond length. It is variable as to the amount of pubescence: the totally glabrous forms occur on the Atlantic slope (Centro, Choapan, Ixtlán, Juchitán, Mixe, Tuxtepec, Villa Alta), whereas the form with hairy rachises and laminar surfaces occurs in Pochutla, Putla, and Tuxtepec. The nomenclature of this species, confused with Blechnum polypodioides (Swartz) Kuhn, which is a synonym of B. fragile (Liebmann) Morton & Lellinger, was clarified by Morton and Lellinger (1967). It is part of the Blechnum occidentale complex (which see for fuller discussion of hybridization in this group), which is in need of extensive genetic study. Walker (1966, 1973, 1985), in careful studies in Jamaica and Trinidad, found the species (as B. unilaterale) to be tetraploid and to hybridize with B. occidentale s.l. producing a sterile tetraploid, which forms large colonies by vegetative reproduction. Difficult to distinguish in some cases, the B. occidentale s.l. x polypodioides hybrids have linear fronds like B. polypodioides but are generally broader (5.5-15 cm wide) than polypodioides, with pinnatifid apices, basal pinnae that are not as greatly reduced as polypodioides but more reduced than occidentale, acuminate and falcate pinnate that are distant in the basal 1/3 of the blade only, and pinnae that are adnate, except for the basal pinnae, which are adnate on the acroscopic side and fully free and cordate on the basiscopic side (fully adnate in polypodioides, fully free and cordate in occidentale). Glabrous specimens corresponding to the hybrid B. occidentale s.s. x polypodioides have been collected in Oaxaca (Rzedowski 21121, NY) in Pochutla at 1700 m, a high elevation for either parent, in Juchitán at 300 m (Hernández G. 1608, NY), and in Choapan (Vera Santos 3376, US) at 200-500 m. Other specimens (all NY unless indicated otherwise) were seen from Veracruz (Kemp, 1906; Fisher 35373; Fink 26 (US); Bourgeau 1438; Purpus 6431 (US)), Guerrero (Dugres, 1905 (US); Hinton 11309, 10100) and Nayarit (Mc Vaugh 12131 (US); Mexia 535; Jones 23490; Lamb 595 (US); Palmer 1941 (NY, US)). Blechnum aduncum Liebmann (Mexic. bregn. 1: 237 (seors. 85). 1849. Type. Mexico. Veracruz: Huatusco, 4500' [1370 m], Liebmann [Pl. Mex. 2324, Fl. Mex. 273, 274] (C!)) and Blechnum confluens Schlechtendal & Chamisso (Linnaea 5: 613. 1830. Type. Mexico. [Veracruz:] Hacienda de la Laguna, Schiede 779 (B! -2 sheets, photos US!, frag. NY!)) appear to represent this hybrid combination. The hybrid combination with pubescent rachises, Blechnum glandulosum x polypodioides has not been found in Oaxaca, although specimens (all NY unless indicated otherwise) have been collected in Jalisco (Mexia 1336, Iltis et al. 567), Guerrero (Langlassé 671, US), Morelos (Rose & Painter 7270) and Veracruz (Purpus 1969). In light of the genetic complexity of this group, Blechnum asplenioides Swartz of South America, with its much narrower blades and no stipe, appears sufficiently distinct to maintain as a species until its relationship with B. polypodioides (which occurs sympatrically in South America and hybridizes with B. asplenioides) can be worked out.

Distribution

Terrestrial (or rarely epiphytic), on open or lightly shaded banks at middle elevations; Centro, Choapan, Ixtlán, Juchitán, Mixe, Pochutla, Putla, Tuxtepec, Villa Alta; 50-1450 (-2500) m. Mexico (Sin, Nay, Gro, Ver, Oax, Chis); Guat to Pan; WI, Trin; Ven & Sur to Braz.

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