36. Diplazium mettenianum (Miquel) C. Christensen, Index Filic. 236. 1905.
江南双盖蕨 jiang nan shuang gai jue
Plants evergreen, small to medium-sized. Rhizome slender, creeping, black-brown, densely scaly at apex; scales black or black-brown, shiny, narrowly lanceolate, ca. 3 mm, thickly membranous, toothed at margin. Fronds distant; stipe brown, base with sparse, narrow lanceolate, brown scales, upward grooved on adaxial side; lamina 1-pinnate or pinnatilobate to pinnatipartite, deltoid, broadly lanceolate-deltoid, or ovate-lanceolate, apex acuminate; pinnae alternate or subopposite, subspreading, sickle-shaped lanceolate or oblong-lanceolate, base truncate or broadly cuneate, stalked or subsessile; veins pinnate, not prominent adaxially, visible abaxially, veinlets simple or forked in basal lobes, ascending. Lamina papery, green or gray-green when dry, both surfaces glabrous; rachis stramineous, glabrous, grooved adaxially. Sori linear, slightly curved, 2-5(-7) pairs per pinna lobe, single or basal sori usually double, medial; indusia light brown, thinly membranous, entire, persistent. Spores reniform, perispore hyaline, ornamentation slightly rugate, not prominently granular.
Forests, streamlets, on wet rocks; 400-1400 m. Anhui, Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan, Zhejiang [Japan, N Thailand, N Vietnam].
Knapp (Ferns Fern Allies Taiwan, 450-451. 2011) considers the dubious name Diplazium agyokuense Tagawa (Acta Phytotax. Geobot. 7: 80. 1938), described from Taiwan, to be a synonym of D. mettenianum. An isotype of D. agyokuense in MICH (MICH1190349) was identified as D. latifrons Alderwerelt by M. G. Price.