Type. Based in part on an illustration in Petiver, Pter. Amer. t. 3, f. 9, 1712, which is a redrawing of t. 29B in Plumier, Traite´ Foug. Ame´r., 1705, illustrating a collection by Plumier from Hispaniola. LINN 1247.1 is this species, but according to Jackson (1912) was added to LINN after 1755. Petiver and Morrison illustrations were also cited.

Unverified, Doubtful, or Mistaken Reports. Col (McVaugh 16096, NY, cited by Mickel, 1992, but not verified). Jal (cited by Va´zquez G. et al., 1995, but not verified, possibly misidentified). Qro (Rzedowski 42867, IEB, cited by Arregui´n et al., 2001, but not verified). Tam (reported by Sharp, 1954, but the specimens are probably B. appendiculatum, as here circumscribed). The B. occidentale complex, in Mexico comprising B. appendiculatum, B. gracile, B. meridense, B. occidentale s.str., and B. polypodioides, is a most difficult group in the Neotropics, both systematically and nomenclaturally.Walker (1966, 1973, 1985) has shown in Jamaica and Trinidad that numerous sterile hybrids exist, but “unlike the situation in most other genera, sterile interspecific hybrids are not always easy to detect on herbarium material using the presence of abortive spores as a criterion. Thespores in this complex seem to be more or less colorless and the abortive ones do not seem to collapse to the extent found in many other fern hybrids.” Many authors (e.g., Murillo, 1968; Stolze, 1981) interpret species in this complex more broadly and as being extremely variable, failing to recognize the occurrence of hybrids. In light of cytological work by Walker in Jamaica and Trinidad, a narrower species concept seems more useful. However, acceptance of hybridization raises new questions— how to recognize and separate possible primary hybrids, allopolyploids, and backcross hybrids. By recognizing B. appendiculatum and B. occidentale as separate species and presenting some new interpretations in the B. gracile-meridense group, we provide hypotheses for further testing. The numerous names and types in this group make it difficult to assign the oldest name to the taxonomic entities, and some changes are likely, once taxonomic circumscription and relationships are understood better. In Mexico, B. occidentale s.str. occurs at 50–900 m, whereas B. appendiculatum occurs at 900–2550 m; this elevational difference is also true in Central America and probably in other parts of the ranges as well. The differences in size (as enumerated in our key and descriptions) appear correlated with differences in elevation and pubescence, and there are relatively few specimens that are difficult to place in one species or the other. Blechnum appendiculatum is much more common in the central, western, and northwestern parts of Mexico. Both B. occidentale and B. appendiculatum are characterized by fully pinnate proximal pinnae, distant pinnae in at least the proximal half of the blades, almost no or only slight reduction in the proximal pinnae, and pinnatifid blade apices. Hybrids with B. gracile can be detected by the smaller number of pinnae and the subconform terminal pinna, whereas hybrids with B. polypodioides (= B. xconfluens; Fig. 55B) have proximal pinnae reduced and partially adnate (acroscopic portion of proximal pinna adnate but the basiscopic portion cordate), falcate pinnae that are adnate over the distal 2/3 of the blades, and narrow, linear blades. These hybrids and their ranges are discussed further under B. gracile and B. polypodioides.Hybrids between B. occidentale and B. polypodioides (Fig. 55B) have linear blades approaching those of B. polypodioides, but blade bases that are intermediate between the putative parents, broader (5–15 cm wide), pinnatifid blade apices, acuminate and falcate pinnae that are distant only in the proximal third of the blades, and adnate pinnae, except at the blade bases where pinnae are adnate on the acroscopic side and free and cordate on the basiscopic side (fully adnate in polypodioides, fully free and cordate in occidentale). Rachises are glabrous in the hybrids, a character by which they can be distinguished from B. appendiculatum x occidentale, discussed below. Specimens corresponding to B. occidentale x polypodioides are the following: Gro (Lorea 1905, MEXU; Lorea 4607, MEXU, UC); Nay (Alava & Cook 1619, UC; Jones 23478, UC; Lamb 591, DS; McVaugh 18848, NY; Mexia 535, CAS, DS, NY, UC); Ver (Bourgeau 1438, B, NY; Bourgeau 3601, UC p.p.; Copeland herb. 47, UC; Fisher 35373, NY; Lamb 591, DS; Purpus 6431, NY, UC, US). Some specimens of this hybrid appear to have well formed spores: Mexia 535. Mickel and Beitel (1988: 87) cited several additional collectionsof this putative hybrid, some of which we now regard as other species or other hybrid combinations. Copeland herb. 47 (UC), also B. occidentale x polypodioides, was determined by Rojas as B. flaccisquama A. Rojas and said to occur from southern Mexico to Panama (type from Costa Rica). Two names based on Mexican types appear to be applicable to this hybrid: Blechnum x aduncum Liebm., Mexic. Bregn. 1: 237 (reprint 85). 1849, pro sp. Type. Mexico. Veracruz: Huatusco, Liebmann s.n. (C); and Blechnum x confluens Schltdl. & Cham., Linnaea 5: 613. 1830, pro sp. Type. Mexico. [Veracruz:] Hacienda de la Laguna, Schiede 779 (B!–2 sheets, photos US!, frag. NY!). Hybrids between B. occidentale and B. appendiculatum are also suspected, and Mickel and Beitel cited several collections from Oaxaca (Mickel 1020a, 4103, 5059, 5023, 6127, NY), and Chiapas (Gittins 4206, NY; Breedlove 29103, NY). Most of these are now judged to be B. appendiculatum because they bear a few hairs on the rachises abaxially, have relatively narrow blades, and grow at middle elevations, above 1350 m. Two abortive-spored specimens, one from Chiapas (Ghiesbreght 277, NY) and one from Guerrero (Hinton 14049, NY), are unusual in having very wide blades (22–24 cm), like B. occidentale, and densely hairy rachises, like B. appendiculatum. Blechnum x falciculatum C. Presl (Epimel. Bot. 106. 1849 [1851]); Type. Mexico. Veracruz: Galeotti 6397 (BR!–3 sheets, photos BM, GH, US!; isotype K!) may apply to this broad-bladed, hairy form.