64. Asplenium capillipes Makino, Bot. Mag. (Tokyo). 17: 77. 1903.
线柄铁角蕨 xian bing tie jiao jue
Asplenium varians Wallich ex Hooker & Greville var. sakuraii Rosenstock.
Plants 3-8(-13) cm tall. Rhizome erect, short, apex scaly; scales dark brown to black, triangular-ovate, margin shortly fimbriate glandular. Fronds caespitose; stipe green, slender, threadlike, 0.3-2.5(-9) cm, subglabrous, adaxially sulcate; lamina triangular to narrowly triangular, (0.6-)1.5-6 × 0.5-2.5 cm, apex obtuse to subacute, 2-pinnate to almost 3-pinnate; pinnae (3-) 5-7 pairs, alternate or basal ones subopposite, stalk slender, threadlike, often at least one stalk with tiny gemma in acroscopic axil, basal pinnae not reduced, broadly ovate to triangular, 4(-12) × 4(-6) mm, pinnate to 2-pinnatifid, upper pinnae trifid to bifid; pinnules 2 or 3(or 4) pairs or 1 pair and a trifid apex, usually bifid, trifid, or simple, basal acroscopic pinnule largest, cordiform or elliptic, 2-3 × 1-2 mm, base cuneate, decurrent on costa, margin entire, apex variable, obtuse or mucronate to acute; pinnae near apex simple or bifid. Veins obscure, anadromously pinnate, simple, 1 per segment or pinnule, with hydathode at end, not reaching margin. Frond herbaceous, green; rachis green, subglabrous, adaxially shallowly sulcate, apex not flagelliform, lamina subglabrous, average guard cell length 45-49 µm. Sori 1 per segment or pinnule, basal to median on subtending vein, subelliptic, 1-2 mm; indusia grayish green, elliptic, membranous, entire, opening toward costa or costule, persistent. Sporangia with 32 spores, perispore lophate (alate), average exospore length 38-42 µm. Plants sexual, diploid: 2n = 72.
Moss cushions on shaded, wet limestone rocks and crevices; 1800-3300 m. ?Gansu, Guizhou, Hunan, ?Shaanxi, Sichuan, Taiwan, Yunnan [Bhutan, India, Japan, Korea, Nepal].
Asplenium capillipes is the smallest species of the genus in China and may be overlooked since it often grows hidden among moss. It is reported from Gansu (Tianshui), Hunan, and Shaanxi (Tibia Shan), but we have seen no specimens; however, it should be noted that large plants of this species are similar to small plants of A. tenuicaule and may be confused with it. Identification of vouchers from Bhutan (Itô in H. Hara, Fl. E. Himalaya, 486-489. 1966) needs verification since some belong to A. fugax, which has a flagelliform apex in contrast to A. capillipes. Plants growing in thick moss cushions may have stipes up to 9 cm. Asplenium capillipes is diploid with n = 36II during meiosis (Mitui, J. Jap. Bot. 45: 84-90. 1970) and 2n = 72 chromosomes in vegetative cells. It is remarkable that it has only 32 relatively large spores per sporangium.