61. Asplenium incisum Thunberg, Trans. Linn. Soc. London. 2: 342. 1794.
虎尾铁角蕨 hu wei tie jiao jue
Asplenium elegantulum Hooker.
Plants 10-30 cm tall. Rhizome short, erect to shortly creeping, occasionally gemmiferous, apex scaly; scales dark brown to black, narrowly triangular, margin fimbriate with short glandular hairs or entire. Fronds caespitose; stipe 4-10 cm, semiterete, basal part abaxially shiny castaneous but upward becoming green, adaxially green and sulcate, with dark brown hairlike scales or subglabrous; lamina lanceolate, 10-27 × 2-4(-5.5) cm, reduced at both ends, apex acute to acuminate, 1- or 2-pinnate; pinnae 12-22 pairs, subopposite to alternate, shortly stalked, lower pinnae gradually reduced, deltoid to semi-orbicular, less than 5 mm, middle pinnae narrowly triangular, 1-2 × 0.6-1.2 cm, apex acute, pinnatipartite to 1-pinnate, its upper segments gradually more adnate to costa; pinnules or segments 4-6 pairs, anadromous, alternate, basal acroscopic pair largest, elliptic or ovate, 4-7 × 3-5 mm, base cuneate, free or decurrent on costa, margin serrate, apex obtuse. Costa distinct, veins obscure, anadromously 2-forked or simple, terminal hydathode distinct and not reaching margin. Fronds herbaceous, often dimorphic and sterile fronds small, green, subglabrous; rachis green or stramineous when dry or base shiny castaneous abaxially, subglabrous, adaxially sulcate, apical part with narrow lateral wings. Sori median to submedian on veinlet, linear, ca. 1 mm; indusia grayish, semi-elliptic, membranous, entire to repand, opening toward costa. Plants sexual, diploid: 2n = 72.
On wet rocks in forests or on buildings or walls; sea level to 1900 m. Anhui, Fujian, Gansu, Guangdong, Guizhou, Hebei, Heilongjiang, Henan, Hunan, Jiangsu, Jiangxi, Liaoning, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [Japan, Korea, Russia].
Asplenium incisum is an ancestral diploid (Kurita, J. Jap. Bot. 35: 269-272. 1960; Rep. (Annual) Foreign Students Coll. Chiba Univ. 41-56. 1967) that hybridized with A. ruprechtii to form a diploid sterile hybrid, which via polyploidy led to the tetraploid A. castaneoviride (= A. kobayashii).