66. Asplenium tenuifolium D. Don, Prodr. Fl. Nepal. 8. 1825.
细裂铁角蕨 xi lie tie jiao jue
Asplenium tenuissimum Hayata.
Plants (10-)20-45 cm tall. Rhizome erect, short, apex scaly; scales dark brown, triangular, margin dentate-fimbriate or entire. Fronds caespitose; stipe semiterete, 7-21 cm, abaxially green or castaneous up to middle, with scales or subglabrous, adaxially shallowly sulcate with supravascular ridge; lamina triangular to ovate, 12-30 × 6-13 cm, apex acute, 2- or 3-pinnate or up to 4-pinnatifid; pinnae 10-16 pairs, alternate, stalk short, basal pair almost not reduced, narrowly triangular, 3-8 × 1.6-3 cm, base truncate to cuneate, up to tripinnatifid, apex acute-acuminate; pinnules (4-)6-12(-16) pairs, alternate, anadromous, shortly stalked, usually acroscopic segment larger, ovate, 1.3-2.8 × 1-1.3 cm, up to 2-pinnatifid; secondary pinnules 3 or 4 pairs, 5-8 × 4-6 mm, base cuneate and decurrent on costule, 2-4-partite, apex obtuse; ultimate segments ovate-lanceolate, ca. 1.5 mm wide, with a single vein, apex acute. Costa slender, adaxially sulcate with supravascular ridge to almost flat when dry, terminal hydathode obvious, not reaching margin. Fronds thinly herbaceous, green; rachis green, adaxially shallowly sulcate with median supravascular ridge or flat, adaxial side of costae or costules with small gemma or plantlet. Sori 1 per ultimate segment, median on subtending vein, elliptic, 1.5-2 mm; indusia whitish to grayish green, linear to elliptic, membranous, entire, opening toward margin costule or central veinlet, persistent. Spores with lophate (alate) perispore. Plants sexual, diploid or tetraploid: 2n = 144.
On wet rocks in mixed forests; 800-2900 m. Guangxi, Guizhou, Hainan, Hunan, Sichuan, Taiwan, S Xizang, Yunnan [Bhutan, India, Indonesia, Malaysia, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam].
"Asplenium concinnum" (Wallich, Numer. List, no. 216. 1829) belongs here but is a nomen nudum and was not therefore validly published (Melbourne Code, Art. 38.1(a)).
Asplenium tenuifolium is common in the Himalaya. It is probably an aggregate of diploid plants with 2n = 72 chromosomes (reported from India; Bir, Curr. Sci. 29: 445-447. 1960; Caryologia 18: 107-115. 1965) and tetraploids (specimens from Guangxi and Guangdong). More studies are needed. Most plants have small dormant buds (one or more) on the adaxial side of the costa (near the first acroscopic costule or more distal) or on the costules. It is often fertile when still young (var. minor S. H. Wu) and can then be confused with A. capillipes (gemmae in axil between costa and rachis) or with A. tenuicaule (without gemmae). The presence and position of its gemmae are diagnostic. We agree with Tagawa (Acta Phytotax. Geobot. 8: 91-100. 1939) that there are no significant differences between A. tenuissimum and A. tenuifolium.