Parablechnum paucipinna A.R.Sm., 2017

Dittrich, Vinícius Antonio De Oliveira, Smith, Alan R. & Gasper, André Luís De, 2017, Parablechnum roraimense and P. paucipinna spp. nov. (Blechnaceae: Polypodiopsida), lectotypification of P. stuebelii, and citation corrections in the family, Phytotaxa 292 (1), pp. 65-73 : 66

Parablechnum paucipinna A.R.Sm. , sp. nov. ( Fig. 1 )

Type:— VENEZUELA. Edo. Bolívar: Sierra de Lema, sector La Escalera, al Este de la carretera, a unos 200 m del salto El Danto en dirección N-S, 05°57’54”N, 61°23’42”W, bosque de galería muy húmedo, 1250–1300 m, 23 Apr 2006, Y. Vivas, B. Holst, J. Tillet & S. Fawcett 1553 (holotype UC-2044673, isotypes SEL, VEN, not seen).

Plants rupicolous; rhizomes compact, concealed by stipe bases and root mass, lacking stolons, caudex ca. 2 cm diam.; rhizome apex scales concolorous, tan to brownish, basifixed or nearly so, lanceolate to ovate-lanceolate with a caudate apex, 8–10 × 1–2.5 mm, margins entire or nearly so; leaves clustered, ca. 35 cm long, the fertile and sterile strongly dimorphic, but similar in length; stipes stramineous, or darkening with age, glabrous above the basal 2–3 cm, sulcate adaxially, with conspicuous transverse wrinkles throughout, the sterile to 20 cm × 2–3 mm, about the same length as the blades, the fertile to 25 cm, twice as long as blades, the basal scales to ca. 6 × 2 mm, entire, lacking marginal setae, not or only weakly pectinate at bases, similar to those of rhizome apices but lighter tan; blades chartaceous, the sterile ca. 20 × 15 cm, deltate, lowest pinnae the longest or nearly so (lacking vestigial proximal pinnae), 1-pinnate, lateral pinnae 4 or 5 pairs, ascending ca. 45 degrees from rachis, to 9 × 1.6 cm, stalked 1–5 mm, bases rounded to cuneate, each pinna with a low, blackish, tuberculiform aerophore at its base, pinna apices abruptly attenuate and minutely toothed at the tips, margins otherwise entire, not revolute; sterile blade apices conform or with a single basal lobe, ca. 8 × 1.6 cm, fertile pinnae delicate, ca. 4 pairs per frond, each ca. 5 cm × 1 mm; rachises stramineous or brownish, with transverse ridges like those of stipes, sulcate adaxially, bearing sparse tan scales ca. 0.5–3 × 0.1–0.4 mm along the costae abaxially, lacking hairs; veins simple or once-forked near their base, free, closely parallel (set ca. 0.5 mm apart midway between costae and pinna margin), without enlarged endings (hydathodes) adaxially, not significantly raised on either side, but darkened abaxially; costae abaxially with rather sparse, filiform to lanceolate tan scales, the larger ones widened and pectinate at their bases, mostly 0.5-1.5 mm long, veins and laminar tissue lacking scales on both sides; sori linear, continuous, parallel to the costae, bearing filiform scales along the costae abaxially; indusia very narrow, glabrous, entire, at least at maturity; spores not seen.

Distribution and habitat:— This species grows on rocks, with fronds clumped, in montane rain forests at ca. 1300 m. The rhizomes are obscured by the compact, fine root mass. Known only from the type.

Etymology:— Named for the few pinna pairs on relatively small fronds.

Notes:— This may be the most delicate species yet described in Parablechnum —relatively thin-textured compared to other species in the genus, and virtually scaleless or with mainly tan, small, filiform, scales on costae and rachises. There are only few pinna pairs, up to ca. 5, in both sterile and fertile fronds; the fertile pinnae are exceedingly narrow, only about 1 mm wide, the narrowest for any known species of Parablechnum . Nearest affinities are uncertain.

Figures

FIGURE 1. Photograph of the holotype of Parablechnum paucipinna (Y. Vivas, B. Holst, J. Tillet & S. Fawcett 1553, UC).