Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Blechnaceae
Species Description - Rhizomes long-creeping, 5-10 mm diam., climbing; rhizome scales bicolorous, reddish brown, with narrow black central stripe, linear-lanceolate, 5-12 x 0.1-0.5 mm, margins with curved teeth 0.1 mm long or less, teeth directed both forward and backward; fronds dimorphic, distant, 80-120 cm long; stipes 1/5-1/3 the frond length, 4-22 cm x 3-5 mm long, glabrous, bicolorous, atropurpureous proximally, often becoming stramineous distally; sterile blades (40-)55-100 x (17-)22-30 cm, pinnatisect (entire to lobed in juvenile forms), largest proximal pinnae not connected to adjacent ones, blade bases abruptly reduced with 6+ pairs of greatly reduced auricles or vestigial pinnae, blade apices entire and with an acuminate tip; rachises bicolorous to concolorous, often atropurpureous in proximal part, glabrous, lacking aerophores at pinna bases; sterile pinnae 20-30 pairs, adnate, slightly falcate, (10-)12-20 x 1-1.8 cm, bases adnate their width or more, decurrent and surcurrent, apices long-acuminate, margins entire, often recurved, both sides glabrous, adaxially with deeply grooved and elevated costae distinct from laminae; veins distinct, simple or 1-forked, with enlarged vein endings visible abaxially; fertile pinnae 20-30 pairs, 8-14(-20) cm 2-4 mm, indusia 1 mm wide, entire.
Lomaria ensiformis Liebm., Mexic. Bregn. 234 (reprint 82). 1849. Struthiopteris ensiformis (Liebm.) Maxon, Contr. U.S. Natl. Herb. 13: 17. 1909. Type. Mexico. Oaxaca: Dist. Chinantla [Dist. Choapan], Teotalcingo, Liebmann s.n. [Pl. Mex. 2342] (C!-2 sheets; isotype US!).
Blechnum ensiforme is most closely related to B. fragile, from which it differs in having much broader blades that are abruptly reduced proximally. Tryon and Stolze (1993) subsumed both B. ensiforme and B. fragile, as well as the related South America B. acutum (Desv.) Mett., under B. binervatum (Poir.) C. V. Morton & Lellinger, from the Lesser Antilles and South America, but we regard all four of these as distinct at species rank. Mickel and Beitel (1988: 82) cited several collections from Mexico (Mickel 991, 1090, 1442, 6561; Hellwig 345; Ventura A. 9365; all from Oaxaca except the last, all NY) and Central America as putative hybrids between B. ensiforme and B. fragile. Mostof these specimens now appear to us to be juvenile, sterile collections of B. ensiforme, which often has a very elongate terminal segment on juvenile fronds. The sole fertile collection of those they cited (Mickel 1090), and the one most likely of hybrid origin, is somewhat intermediate between the two species, but perhaps more like B. ensiforme in sterile blade shape (compare Mickel & Beitel, 1988, f. 123B with 125C); this collection does indeed have partially malformed spores, but a significant proportion of the spores appear normal.
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