20. Adiantum induratum Christ, J. Bot. (Morot), ser. 2. 1: 265. 1908.
圆柄铁线蕨 yuan bing tie xian jue
Plants 15-40 cm tall. Rhizomes erect, short, scales dense, dark brown. Fronds clustered; stipe brown when young, black when old, glossy, 4-20 cm, less than 1.5 mm in diam., adaxially grooved with stiff brown hairs inside, terete when old, glabrescent; lamina 2-4-pinnate, broadly ovate in outline, 10-20 × 6-10 cm; pinnae 2-4 each side, obliquely spreading, stalked; rachis, costae, and stalks dark brown and glossy, abaxially glabrous, adaxially densely brown-yellow pubescent; basal pair of pinnae largest, narrowly ovate in outline, 4-9 × 2-4 cm, stalks 1-1.2 cm, 2- or 3-paripinnate; outer pinnae progressively shorter; pinnules 2 pairs per pinna, alternate, oblique upward; stalk ca. 3 mm, articulate at apex, persistent after pinnules fall; pinnules of fertile fronds subrounded, 5-9 × 8-11 mm, subleathery, dark brown-yellow or dark brown-green, abaxially sometimes slightly glaucous, both surfaces glabrous, base broadly cuneate or truncate, inner and lower margins straight and entire, outer and upper margins rounded or subrounded, entire or few sinuate; pinnules of sterile fronds slightly larger, oblong, 9-12 × 11-16 mm, bases broadly cuneate, entire, outer and upper margins undulately lobed, denticulate; distal pinnules similar but slightly smaller; terminal pinnules: stalks 2-4 mm, blades flabellate, slightly larger than lower pinnules. Veins multidichotomously forked, reaching margins, visible on both surfaces. Sori (1 or 2 or)4-6 on ultimate pinnules, horizontally attached at upper margins; false indusia dark brown, reniform, broadly linear, or oblong, leathery, upper margins truncate or slightly depressed, entire, persistent.
Acidic soil of forests by roadsides or forest margins; 100-800 m. Guangdong, Guangxi, Hainan, Yunnan [Vietnam].