5. Diplazium crassiusculum Ching, Lingnan Sci. J. 15: 279. 1936.
厚叶双盖蕨 hou ye shuang gai jue
Athyrium crassiusculum (Ching) T. J. Liu; Diplazium crassiusculum f. simplex Ching; D. donianum (Mettenius) Tardieu var. biserrulatum Tardieu.
Rhizome erect or oblique, black-brown, woody, stiff, apex with dense scales; scales dark black, glossy, lanceolate, thick, small serrate at margin; fronds caespitose, 1-pinnate fertile frond more than 1 m; stipe black at base, upward gray-stramineous, 40-60 cm, 3-5 mm in diam., base like rhizome, densely scaly, upward glabrous, grooved on abaxial side; lamina 1-imparipinnate, elliptic, 30-50 × 16-24 cm; lateral pinnae often 2-4 pairs, all subequal in size, alternate or basal pinnae subopposite, oblique, shortly stalked (stalk of basal pinnae 6-8 mm), narrowly elliptic, narrowly ovate-lanceolate, or broadly linear-lanceolate, 16-23 cm, middle 3.5-4.4 cm wide, base rounded-cuneate, margin in lower part of pinna often subentire or slightly repand, from middle to apex thin, serrate, apex long acuminate; apical pinna similar to lateral pinnae or nearly so, base often asymmetrical; costae prominent, rounded, occasionally with brown linear small scales on abaxial side, shallowly grooved on adaxial side; veinlets all prominent, slightly oblique, 3 or 4 per veinlet group, thin, reaching laminar margin. Lamina firmly herbaceous, brown-green when dry. Sori and indusia long linear, often single on acroscopic veinlets of each veinlet group, oblique, from costa to ca. 5 mm inside margin.
Evergreen broad-leaved forests and shrubs; 200-1700 m. Fujian, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, N Taiwan, Zhejiang (Taishun) [Japan].
Fertile fronds of young plants of Diplazium crassiusculum are sometimes simple, elliptic-lanceolate with cordiform, slightly asymmetrical bases, or 1-pinnate with only 2 or 3 pinnae.