Blechnum rosenstockii Copel.

Rhizome forming a slender caudex less than 1 cm diam., erect up to 1 m, but tending to fall and be suberect, caudex scaly, scales linear, acuminate, entire, or occasionally toothed, 0.5-1.2 by 0.1-0.15 cm, ranging from mid brown to reddish brown shiny concolorous to mostly bicolorous with a darker zone of cells in the central region. Fertile and sterile fronds of similar dimensions, erect, 20-60 by 2.5-8 cm. Stipes short and slender 3-15 by 0.1-0.2 cm, brown to reddish brown, densely scaly at the base and with a few persistent scales above, stipe scales like those of the rhizome but grading to broader, shorter, paler, more peltate scales sometimes with irregularly tooth­ed margins. Lamina linear narrowly elliptic, widest above the mid-region and very gradually tapering to the base, pinnatisect, pinnae up to 70 pairs, including triangular lobes at apex and base; lamina of living material dark-green above, mid green below. Rhachis and costae brown, greenish brown or reddish brown, often paler on underside, scaly at base and with a few persistent pale reddish brown entire acuminate scales above and some broader thin concolorous scales, some with toothed margins. Sterile pinnae narrow linear to narrowly elliptic, 1.6-3.2 by 0.3-0.6 cm, broad slightly decurrent base adnate to rhachis, thinly coriaceous to coriaceous, margins often finely revolute and ranging from entire to dentate with shallow to deep teeth or lobes angled towards the pinna apex, veins unevenly furcate, sometimes trifurcate, each branch terminating on the upper surface either in the mid-region or submarginally in a linear clavate gland, basal pinnae reduced to slightly distant triangular outgrowths, apical pinnae progressively reduced to adnate pinnatifid lobes, terminal segment larger than the lateral pinnae and dentate. Fertile pinnae slightly narrower than the sterile, shortly apiculate, sometimes a little constricted before the slightly decurrent adnate base, fertile pinnae below the mid-lamina region with sterile adnate decurrent bases; sori orange-brown, occupying the whole width of the undersurface except for sterile zone on either side of the midrib at the rhachis, basal pinnae often completely sterile. Spores orange-brown, 54.8 by 36.8 µm (from 5 herbarium specimens), perine verrucose to very deeply verrucose, verrucae covered with scabrous layer which varies in its persistence, surface smooth to finely reticulate at the base of and sometimes entirely covering verrucae, exine smooth to granulose.