单边膜叶铁角蕨 dan bian mo ye tie jiao jue

Asplenium cataractarum Rosenstock (1915), not Blume (1828); Hymenasplenium cataractarum N. Murakami.

Plants 25-40 cm tall. Rhizome shortly creeping, 2-3 mm in diam., apex densely scaly; scales castaneous to dark brown, narrowly triangular; phyllopodia distinct, ca. 2 mm, ca. 10(-40) mm apart. Fronds grayish green when dry, herbaceous; lamina 1-pinnate, narrowly triangular to lanceolate, 10-20 × 3-5 cm, widest in basal 1/3, gradually narrowing toward apex, glabrous; stipe shiny, purple, 10-25 × 0.05-0.15 cm, subglabrous, base sparsely scaly; rachis shiny, purplish abaxially, adaxial side grooved and with 2 grayish green narrow wings; pinnae almost sessile to shortly stalked with purple rachis color extending via stipicel up to 3 mm onto basal part of costa abaxially, 15-25 pairs, alternate, usually ascending, falcate to trapeziform, 2-3.5 × 0.6-1 cm, base asymmetrical, acroscopic side truncate, basiscopic side attenuate-cuneate with ca. 1/2 cut away, acroscopic margin serrate, teeth usually not retuse, pinna apex (sub)acute. Veins forking and terminating in marginal teeth, only 1 or 2 basal basiscopic veins lacking. Sori linear, 2-3 mm, supramedial to (sub)marginal, indusia brownish, linear, membranous, entire, opening toward costa. Plants diploid, sexual with 2n = 78.

Usually on wet rocks near or in streams in forests. Jiangxi, Taiwan, Yunnan [Japan].

Due to the previous confusion in the Hymenasplenium unilaterale s.l. group, the distribution of H. murakami-hatanakae is not well known. As an ancestral diploid, it may have played an important role in the reticulate evolution of Hymenasplenium in Asia and along the Pacific. However, the elucidation of relationships in the "unilaterale" group will require much more micromorphological and molecular studies. True H. unilaterale may be largely absent from India, the Himalaya, and the Pacific region, where its nomenclature urgently needs to be brought in line with data published by Cheng and Murakami (J. Plant Res. 111: 495-500. 1998).

Asplenium pubirhizoma Ching & Z. Y. Liu, described from Sichuan, may represent a species of its own although it was considered a synonym of A. unilaterale s.l. by Wu (FRPS 4(2): 38. 1999); it is similar to Hymenasplenium murakami-hatanakae but differs in its gray, hairy scales and its more medial sori.