Asplenium mesosorum Makino, Bot. Mag. (Tokyo) 12: 120. 1898; Athyrium mesosorum (Makino) Makino; Diplazium mesosorum (Makino) Koidzumi.

Rhizome long or shortly creeping, apex and stipe base densely scaly; scales brown, lanceolate, clathrate, membranous, hyaline, with long multicellular marginal hairs; fronds approximate. Fertile fronds 50-60 cm; stipe pale castaneous or red-brown, shiny, 20-40 cm, 2-3 mm in diam., upward glabrous; laminae 2- or 3-pinnate with pinnules or ultimate pinnules pinnatipartite, broadly ovate to deltoid, 30-40 × 15-25 cm at base, apex abruptly narrowed, acuminate; pinnae ascending, narrowly ovate to broadly lanceolate, apex long acuminate; basal pair largest, 15-20 ´ 4.5-10 cm, with stalk 2-4 cm; pinnules 8-15 pairs, alternate, subspreading, ovate-deltoid, base asymmetrical (acroscopic base subtruncate, basiscopic base broadly cuneate), lower pinnules stalked, usually basiscopic pinnules longer than acroscopic pinnules, ca. 8 × 3 cm, pinnatilobate or nearly pinnate; pinnule lobes slightly oblique, ovate-deltoid or oblong, connate to each other with narrow wings, pinnatilobate to pinnatipartite or nearly pinnate, apex rounded-obtuse; ultimate pinnules obtuse at apex, shallowly toothed at margin. Veins prominent on both sides, pinnate, veinlets simple or forked; lamina green or brown-green, thinly herbaceous or submembranous, glabrous on both surfaces; lower part of rachis and costae pale castaneous or red-brown, upper part stramineous, shiny. Sori lunate, narrowly elliptic, single and costular on basal acroscopic veinlets; indusia pale green when young, becoming pale brown when mature; perispore with irregularly warty ornamentation.

Wetlands in forests; 100-1000 m. Hubei (Badong), Jiangsu (Yixing), Zhejiang (Lin’an) [Japan, Korea].