Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Blechnaceae
Genus Description - Terrestrial, hemiepiphytic or epiphytic; rhizomes longcreeping to compact and erect, sometimes forming trunks, scaly, often stoloniferous and forming large colonies; fronds monomorphic or dimorphic, small to medium-sized (to large); stipes adaxially grooved, stramineous to atropurpureous, glabrous to sparsely or moderately scaly, non-articulate to rhizomes; fronds mostly pinnatifid to pinnate, rarely undivided, margins entire to serrulate, young expanding fronds usually reddish; blades glabrous, occasionally with small scales on costae and veins, chartaceous to coriaceous; veins of sterile blades free, parallel, simple or 1–2-forked, running to or nearly to margins; sori costal, on commissural veins (connecting adjacent veins) parallel and close to costae, indusiate; indusia directed inwardly, opening toward costae, entire to laciniate; spores bilateral, perispore inconspicuous to winged; x=28, 29, 31, 32, 33, 34, 36.
Struthiopteris Weiss, Pl. Crypt. Fl. Gott. 286. 1769. Type: Struthiopteris spicant (L.) Weiss [=Blechnum spicant (L.) Sm.]. Lomaria Willd., Ges. Naturf. Freunde Berlin Mag. Neuesten Entdeck. Gesammten Naturk. 3: 160. 1809. Type: Lomaria nuda (Labill.) Willd. [= Onoclea nuda Labill.] = Blechnum nudum (Labill.) Luerss. Parablechnum C. Presl, Epimel. Bot. 109. 1849 [1851]. Blechnum sect. Parablechnum (C. Presl) T. Moore, Index Fil. xxv. 1857. Type: Parablechnum procerum (G. Forst.) C. Presl [= Osmunda procera G. Forst.] =Blechnum procerum (G. Forst.) Sw. Lomaridium C. Presl, Epimel. Bot. 154. 1849 [1851]. Lomaria sect. Lomaridium (C. Presl) J. Sm., Hist. Fil. 303. 1875. Type: Lomaridium plumieri (Desv.) C. Presl [= Lomaria plumieri Desv.] = Blechnum binervatum (Poir.) C. V. Morton & Lellinger.
Blechnum is the largest genus of the family Blechnaceae and is related to Woodwardia. The nearly 200 species are primarily tropical, with four boreal-temperate species and several australtemperate species. There are 15 species in Mexico; most are widespread, extending into Central and South America. The genus has sometimes been subdivided on the basis of monomorphic (Blechnum) vs. dimorphic fronds (Lomaria), but there are several groups of dimorphic species, each of which could be justified as a distinct genus: sect. Lomariocycas (J. Sm.) C. V. Morton, with stout trunks (Costa Rica to Bolivia); sect. Parablechnum (C. Presl) T. Moore, with stout, short, erect rhizomes (e.g., B. schiedeanum); an unnamed group, with erect, slender trunks, pinnatifid sterile blades, and reduced proximal pinnae (e.g., B. divergens, B. lehmannii, B. wardiae); and sect. Lomaridium (C. Presl) comb. ined., with climbing rhizomes and toothed rhizome scales (e.g., B. fragile, B. ensiforme). The monomorphic species seem closely allied to each other, with the exception of B. serrulatum (in sect. Diafnia (C. Presl) J. Sm.). Recent molecular work by Cranfill (2001) has demonstrated that a monophyletic Blechnum can be obtained only by the recognition of many smaller genera, e.g., Lomaria, Lomaridium, Lomariocycas, and Parablechnum, mentioned above. Such a re-circumscription would restrict the application of Blechnum to the group of monomorphic species allied to B. occidentale. The Mexican species of Blechnum are characterized by adaxially grooved stipes and rachises, with the grooves usually extending into the costae, except in smaller species like B. stoloniferum. Most Mexican species have enlarged vein endings on the blade surfaces adaxially, except B. fragile and B. ensiforme, which have vein endings visible only on the abaxial surfaces, and B. serrulatum, in which the veins run into cartilaginous pinna margins. Among the monomorphic blechnums, hybrids appear to be numerous, as judged by intermediate morphology and malformed spores. Many of these species and hybrids in this group are relatively common in disturbed and semi-disturbed habitats, such as along roadsides and trails. Definitive assignment of parentage of putatively hybrid plants must await further morphological, cytological, and electrophoretic studies, in many cases.