88. Asplenium tenerum G. Forster, Fl. Ins. Austr. 80. 1786.
膜连铁角蕨 mo lian tie jiao jue
Asplenium caudatum Cavanilles (1802), not G. Forster (1786); A. elongatum Swartz (1806), not Salisbury (1796); A. productum C. Presl; A. tenerum var. terminans Kunze ex Mettenius; Darea tenera (G. Forster) Sprengel.
Plants 30-65 cm tall. Rhizome erect, short, apex scaly; scales blackish brown, with pale reddish brown edges, triangular, 3-5 mm, margin fimbriate to subentire. Fronds caespitose; stipe green or stramineous when dry, 12-30 cm, adaxially sulcate with median supravascular ridge, base scaly, or subglabrous; lamina narrowly triangular to linear, 20-38(-50) × 7-10(-14) cm, apex caudate, 1-pinnate to rarely bipinnatifid; pinnae 15-25(-35) pairs, subopposite to alternate, shortly stalked, lower pinnae not reduced, narrowly triangular, 3-5 × 1-1.5 cm, simple, base asymmetrical, acroscopic side truncate, basiscopic side cuneate, margin crenate, apex acute or obtuse. Costa stramineous, raised on both sides, venation obvious, pinnate, basal acroscopic vein 2-4 times forked, other veins simple, not reaching margin. Fronds subleathery, grayish green when dry; rachis stramineous when dry, with hastate-stellate fibrillar scales or subglabrous, sulcate with median supravascular ridge on adaxial side, sometimes gemmiferous near apex. Sori median on veins, linear, ca. 3 mm; indusia whitish to gray-brown, linear, membranous, entire, opening toward costa.
On rocks in dense forests; 400-1000 m. Hainan, Taiwan [India, Indonesia, Japan, Korea, Malaysia, Myanmar, Philippines, Sri Lanka, Vietnam; Pacific islands].
Asplenium tenerum is a variable taxon. Plants with gemmiferous rachis are known from China (Taiwan), Indonesia, Japan (Ryukyu Islands), and Malaysia and may represent a different taxon. As presently circumscribed, this species is probably an aggregate needing further monographic study. Plants with pinnate-pinnatisect fronds, similar to A. sampsonii but without reduced basal pinnae, most probably belong to this species. Indian plants are tetraploid, but the chromosome number of Chinese material is unknown.