Morfología, caracterización y distribución geográfica de Blechnum cordatum (Blechnaceae-Pteridophyta).

Résumé

Morphology, characterization, and geographical distribution of Blechnum cordatum (Blechnaceae-Pteridophyta). Specimens of Blechnum cordatum from localities of its large geographical area were analized. The species grows in Mesoamerica, Antillas and South America, from Venezuela and Colombia to Bolivia, SE and centre of Brazil, Paraguay, Argentina, centre and S of Chile, and Juan Fernández Islands. Blechnum cordatum is a tolerant, not vulnerable species, with large sporophytes; erect, scaly rhizomes; dimorphic fronds with scaly stipes and axes; lanceolate sterile laminae with lanceolate to oblong, coriaceae, finely denticulate to serrate, superficially scaly and hairy, attached by costa (peciolulate) pinnae, with cuneate- truncate to subcordate or auriculate bases, and narrowly lanceolate fertile laminae with vegetative tissue of pinnae reduced to the portion which support the undulate to erose indusia and continuous coenosorus. Veins are free, simple, geminate and furcate, the latter ramdomly dividing at different distances from the costa, all ending in large, active hydathodes. Aerophores, located only at the base of pinnae, may be absent. Spores have a cristate-reticulate perispore with filiform, ramified processes, and a smooth to granulate exospore. Based on this study, a new description of Blechnum cordatum, and its taxonomy is presented, along with comments on affinities with other neotropical and paleotropical species of the genus.