34. Adiantum capillus-veneris Linnaeus, Sp. Pl. 2: 1096. 1753.
铁线蕨 tie xian jue
Adiantum capillus-veneris f. dissectum (M. Martens & Galeotti) Ching; A. capillus-veneris f. fissum (Christ) Ching; A. capillus-veneris var. fissum Christ; A. capillus-veneris f. lanyuanum W. C. Shieh; A. capillus-veneris var. trifidum Christ; ?A. lingii Ching; A. michelii Christ; A. subemarginatum Christ, p.p.; A. tenerum Swartz var. dissectum M. Martens & Galeotti.
Plants terrestrial or epilithic, 10-40 cm tall. Rhizomes creeping, slender, scales dense, brown, lanceolate, margins entire. Fronds remote or closely spaced; stipe castaneous-black, glossy, 3-20 cm, slender, base covered with same scales as rhizome, distally glabrous; lamina mostly 2-pinnate below middle, 1-pinnate above middle, ovate-triangular in outline, 6-25 × 8-16 cm, base cuneate, apex acute; pinnae 3-5 each side, obliquely ascending, stalk up to 15 mm; rachises, costae, and stalks same color as stipes, slightly zigzag, color passing into lamina base; basal pair of pinnae larger, 1(or 2)-pinnate, narrowly ovate in outline, 3-9 × 2.5-4 cm, apex obtuse; pinnae from second pair upward all similar but progressively smaller; pinnules 2-4 pairs per ultimate pinna, alternate, obliquely ascending; stalk castaneous-black, 1-2 mm, slender; blade subequal in size or basal pair slightly larger, 12-20 × 10-15 mm, thinly herbaceous, green or dark brown-green, both surfaces glabrous, base cuneate, sides entire, upper margin rounded, 2-4-lobed or divided into twiglike segments; sterile pinnules with apex obtuse, with marginal teeth broadly triangular or erose; fertile segments with apex truncate, straight or slightly depressed, entire or with erose teeth on both sides; terminal pinnules flabellate, usually larger, base narrowly cuneate, stalks up to 1 cm. Veins multidichotomously forked, reaching margins, visible on both surfaces. Sori 3-10 per pinnule, on apices of lobes of upper margin; false indusia yellowish green, brown when old, narrowly reniform or orbicular-reniform, membranous, upper margins flat and straight, entire, persistent. Perispore thickly granular.
On limestone near running streams, bottom of limestone caves, cliffs wet with dripping water; 100-2800 m. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Japan, Vietnam; widely distributed in temperate and tropical regions in Africa, America, Asia, Europe, Oceania].
Material of Adiantum lingii Ching (Acta Phytotax. Sin. 6: 341. 1957, from Sichuan) has not been seen and is placed here on the basis of the protologue. It was compared with A. capillus-veneris but differed by the smaller pinnules that dry olive-green, each with 4-6 sori with orbicular to orbicular-reniform false indusia.
Plants with ultimate pinnules shallowly divided on upper margins have been treated as Adiantum capillus-veneris f. capillus-veneris, while plants with ultimate pinnules deeply divided into several lobes have been treated as f. dissectum.
Adiantum capillus-veneris is an indicator of calcareous soil.
The whole plant is used in traditional Chinese medicine.