小膜叶铁角蕨 xiao mo ye tie jiao jue

Asplenium subnormale Copeland in Perkins, Fragm. Fl. Philipp. 183. 1905.

Plants 15-20 cm tall. Rhizome long creeping, ca. 3 mm in diam., apex scaly; scales narrowly triangular to triangular. Fronds remote, up to 5 mm apart, brown grayish green when dry, herbaceous, subglabrous; stipe slightly shiny, dark purple-brown to black abaxially, 5-6 cm, sparsely scaly to subglabrous; lamina 1-pinnate, ovate-triangular, 9-12 × 5-6 cm, base truncate and slightly reduced, apex acute; rachis grayish green, base slightly shiny and purple, with scales or subglabrous; pinnae up to 10 pairs, distinctly stalked, stipicel broadly falcate-trapeziform, up to 0.3 cm, middle pinnae 2.5-3 × 0.8-1.3 cm, dimidiate, apex obtuse, base asymmetrical, acroscopic side semicordate to truncate and parallel to rachis, basiscopic side of basal pinnae excavate (cut away), in middle pinnae becoming narrowly cuneate and entire, acroscopic margin serrate, teeth not retuse; pinnae spreading to ascending, basal pinnae slightly reduced and deflexed. Veins distinct, forking and free, ending below marginal tooth, basiscopic side with 1(or 2) vein(s) lacking. Sori medial, linear, 2-6 mm; indusia persistent, pale brown, semi-elliptic to linear, membranous, entire, mainly opening toward costa.

Moss-covered rocks in shaded humid ravines in forests; near sea level to 1000 m. Taiwan, SW Yunnan [Indonesia, Japan, Malaysia, Philippines].

The description of Hymenasplenium subnormale is based on the Yunnan material, which might represent an undescribed species. The type of H. subnormale, collected in the Philippines, is a smaller plant in general and differs also essentially from other members of Hymenasplenium in its venation pattern with none of the basiscopic veins lacking (isotypes in MICH!, B!). Morphological variation within this taxon has been pointed out by Holttum (Revis. Fl. Malaya 2: 437-438. 1954) and Iwatsuki (Acta Phytotax. Geobot. 27: 51. 1975; Fl. Jap. 1: 108. 1995). Mitui et al. (Amer. J. Bot. 76: 1691. 1989) reported a base chromosome number of x = 38 instead of the "normal" x = 39 for most of the other species in the genus. They also found both diploids (n = 38, 2n = 78) and tetraploids (n = 78) in a collection from Ceram (Indonesia). Cheng and Murakami (J. Plant Res. 111: 495-500. 1998) reported a related diploid taxon ("Asplenium latipinnum," nom. nud.) with n = 39 from Yunnan, differing by its more inframedial sori, but without formally publishing it as a new taxon. This taxon is thus clearly an aggregate, and plants from outside of the Philippines may represent one or more related species. The whole complex needs a thorough revision.