圆齿铁线蕨 yuan chi tie xian jue

Adiantum venustum D. Don var. breviserratum Ching, Acta Phytotax. Sin. 6. 335. 1957.

Plants 20-30 cm tall. Rhizomes creeping, scales dense, brown, lanceolate. Fronds tufted or approximate; stipe castaneous-brown, glossy, 10-20 cm, base with same scales as rhizome, distally smooth; lamina 3- or 4-pinnate, subovate-triangular in outline, ca. 15 × 10 cm, apex acuminate; primary pinnae 5 or 6 each side, spreading obliquely upward, with stalk 2-6 mm; basal pair of pinnae largest, 2-pinnate, ovate or subovate-triangular in outline, 7-9 × 2.5-4 cm, apex obtuse; secondary pinnae 4 or 5 pairs, basal pair of pinnae largest, 1-pinnate, broadly ovate in outline, 2.5-3.5 × ca. 1.5 cm, apex obtuse; pinnules 2-4 pairs per ultimate pinna; stalk silklike; blade obovate or narrowly flabellate, 3-6 × 3-6 mm, progressively smaller distally, thinly herbaceous, grayish green, both surfaces glabrous, base cuneate, bilateral sides entire, upper margins rounded and crenate. Veins multidichotomously forked, reaching teeth of upper margin of pinnule, visible on both surfaces. Sori 1 per pinnule, horizontally attached at upper margin; false indusia brownish, suborbicular or rectangular, membranous, upper margins flat and straight, upper margins flat and straight, entire, persistent.

● On limestone; 2400-3500 m. Xizang, N Yunnan.