尖峰岭膜叶铁角蕨 jian feng ling mo ye tie jiao jue

Type: China. Hainan: Ledong County ("Kan-en District"), Jianfeng Ling ("Chim Fung Ling"), "near Sam Mo Watt village, Shan Mong," 23 Apr 1934, S.-K. Lau 3841 (holotype, PE).

Planta morphologia Hymenasplenio obscuris. Rhizoma longe repens, squamis 2.5-3.5 mm longis et ca. 0.25-0.7 mm latis. Petiolus rachisque pro parte abaxiali griseo-virides; lamina papyracea. Sori 2-3 mm longi. Sporae exosporium 29-34 µm longum.

Plants 20-50 cm tall. Rhizome long creeping, 3-5 mm in diam., apex scaly; scales narrowly triangular to triangular, 2.5-3.5 mm. Fronds remote, 3-5 mm apart, grayish green when dry, papery to herbaceous, subglabrous; stipe dull green to grayish green when dry, not shiny or purple, (5-)15-20(-25) cm, sparsely scaly to subglabrous; lamina 1-pinnate, narrowly ovate-triangular, 20-25 × 5-10 cm, base truncate, apex acuminate to caudate; rachis grayish green, subglabrous; pinnae 15-30 pairs, sessile to stalked, trapeziform-falcate, middle pinnae 2.5-4 × 0.8-1.8 cm, dimidiate, apex obtuse to subacute, base asymmetrical, acroscopic side truncate and parallel to rachis, basiscopic side excavate to narrowly cuneate, entire, acroscopic margin (bi)serrate, teeth not retuse, suprabasal pinnae spreading to ascending. Veins distinct, forking and free, ending below a marginal tooth, basiscopic side with (3 or)4 or 5 veins lacking. Sori medial to supramedial, linear, 2-3 mm; indusia persistent, allantodioid, double and consisting of an outer and an inner part (between lamina and sporangia), pale brown, semi-elliptic to linear, membranous, entire, opening toward costa.

Shaded forest floors near water courses; 500-800 m. Guizhou, Hainan, Taiwan, Yunnan [N Thailand, N Vietnam].

Murakami (J. Plant Res. 108: 261. 1995) used, but did not validly publish, the name "bilabiatum" for this taxon; he reported it from N Thailand to N Vietnam and from Taiwan. Hymenasplenium pseudobscurum is an aggregate of a diploid and a tetraploid taxon (Kato et al., Bot. Mag. (Tokyo) 105: 105-124. 1992; Cheng & Murakami, J. Plant Res. 111: 498. 1998), and further research is needed to discriminate between them. Molecular studies of Murakami (loc. cit.: 266) demonstrated that H. pseudobscurum is closely related to H. obscurum.

The special allantodioid sorus, with an inner and an outer indusium, is also found in Hymenasplenium bivalvatum (B. K. Nayar & Geevarghese) Viane, comb. et stat. nov. (Basionym: Asplenium unilaterale Lamarck var. bivalvatum B. K. Nayar & Geevarghese, Fern Fl. Malabar, 292. 1993; 双盖膜叶铁角蕨 shuang gai mo ye tie jiao jue), a sexual diploid with 2n = 78 chromosomes and differing from H. pseudobscurum by the abaxial color of its stipe (shiny and dark purple to black). The occurrence of H. bivalvatum in S China needs to be verified; however, according to Ralf Knapp (pers. comm.), most Taiwanese specimens formerly identified as H. obscurum are H. pseudobscurum.