Blechnum occidentale

Smith, Alan R. & Kessler, Michael, 2018, Prodromus of a fern flora for Bolivia. XXXIII. Blechnaceae, Phytotaxa 334 (2), pp. 99-117 : 104

Blechnum occidentale L., Sp. Pl. 2: 1077. 1753.

Range:— Florida; Mexico to Bolivia (BE, CH, CO, LP, SC, TA), Paraguay, and northern Argentina.

Ecology:— Common; terrestrial and saxicolous in humid forests, along streams, on banks, in thickets, among and on rocks, often in large colonies in damp and shaded sites; to 1500 m.

Notes:— A very variable, tetraploid species. Specimens with thinner-textured blades held horizontally over the ground, reflexed basal pinnae, and acroscopically adnate bases of the proximal pinnae have been called Blechnum austrobrasilianum de la Sota in herbaria, but we concur with Sundue (2011) that it is uncertain whether this form is sufficiently distinct from B. occidentale to warrant species status.

Blechnum occidentale presumably hybridizes with B. appendiculatum , B. gracile , and possibly other species. Hybridization is certainly the easiest way to explain the apparent, not so common, intermediates in this weedy group, and one such hybrid, involving B. occidentale , has been well documented from Trinidad ( Walker 1985).

Putative hybrids with B. gracile probably correspond to the taxon named Blechnum ×caudatum Cav. that is characterized by 5–10 pinna pairs and blade apices abruptly reduced to a segment 2–3 times as long as the distal pinnae. This form reproduces mostly vegetatively but possibly also sexually and may perhaps best be treated as a distinct species of hybridogenic origin.

The putative hybrids with B. polypodioides are recognized by narrow, linear blades, reduced, acroscopically adnate, basiscopically cordate proximal pinnae, and falcate, adnate median pinnae. The names Blechnum ×aduncum Liebm. , pro sp. and B. × confluens Schltdl. & Cham. , pro sp., may apply to this form ( Mickel & Smith 2004). Murillo (1968) and Tryon & Stolze (1993) applied the name B. confluens in a different sense, to include what we and most others call B. polypodioides .