南川双盖蕨 nan chuan shuang gai jue

Basionym: Allantodia nanchuanica W. M. Chu, Acta Phytotax. Sin. 21: 219. 1983; A. anshunica P. S. Wang.

Plants evergreen, medium-sized to large, up to 2 m tall. Rhizome erect, ascending, or decumbent, to 54 cm, surrounded by dense aerial roots, 10 cm in diam. (including aerial roots), densely scaly at apex; scales dark brown to black, lanceolate to linear-lanceolate, margin denticulate, apex long acuminate; fronds approximate or caespitose, rarely distant. Fertile frond 60-150 cm; stipe light green, blackish at base, 18-57 cm, 2-5 mm in diam., covered with scales; scales lanceolate, often easily deciduous leaving greenish long-conical stalklets, base cordate, margin densely denticulate, apex long acuminate; lamina 2-pinnate, broadly ovate-deltoid, 50-100 × 30-60 cm, apex acuminate; pinnae 8-10 pairs, mostly alternate, rarely subopposite, ascending; lower pinnae broadly oblong-lanceolate, up to 46 × 19 cm, with stalk up to 4 cm, apex acuminate; pinnules up to 10 pairs, alternate, spreading, lanceolate to broadly lanceolate, up to 8 × 2 cm, base truncate, symmetrical or nearly symmetrical, sessile, pinnatilobate to pinnatifid, apex acuminate; pinnule lobes up to 10 pairs, contiguous, ascending, margin entire or slightly crenate, apex rounded; veins pinnate, veinlets up to 7 pairs per pinnule lobe, ascending, mostly simple, rarely forked. Lamina thinly papery when dry, green, darker adaxially, subglabrous on both surfaces; rachis and costa light green. Sori shortly linear, less than 4 pairs per lobe, basal sori long, inframedial from midrib to 3/4 length of veinlet, other sori shorter, medial, mostly single or double on basal acroscopic veinlets; indusia brown when mature, membranous, entire. Spores reniform, perispore not prominent, glabrous on surface.

● Calcareous mountains, beside streamlets; 600-800 m. Chongqing (Jinfo Shan), Guizhou (Anshun).

Diplazium nanchuanicum is similar to D. simile but differs by the narrow lamina, linear-lanceolate, loose scales, and glabrous costae and costules. Allantodia anshunica P. S. Wang (Pterid. Fl. Guizhou, 64. 2001), with aerial roots on rhizome and stalklets on stipe scales, characters not present in the protologue of D. nanchuanicum, is confirmed to be a synonym of D. nanchuanicum by reviewers P. S. Wang and W. M. Zhu.