白垩铁线蕨 bai e tie xian jue

Adiantum greenii Ching; A. leveillei Christ.

Plants terrestrial, 4-14 cm tall. Rhizomes erect, short, scales black subulate-lanceolate, margins denticulate. Fronds clustered; stipe castaneous-black, glossy, 1-6 cm, slender, glabrous; lamina 1-pinnate, oblong or ovate-lanceolate in outline, 3-6 × 2-2.5 cm; costae and stalks same color as stipes; pinnules 2-4 pairs, 1-2 cm apart, alternate, obliquely spreading upward; stalk up to 3 mm (ca. 1/5 as long as pinnae or shorter), articulate, persistent after pinnules fall; blade broadly obovate or broadly ovate-triangular, ca. 1 × 1 cm, papery, abaxially glaucous, adaxially grayish green, both surfaces glabrous, base rounded-cuneate or rounded, both sides slightly undulate, apex rounded, with 1(or 2) shallow sinus, entire; veins dichotomously branching, and reaching cartilaginous margins, visible on both surfaces. Sori 1(or 2) per pinna; false indusia brown, reniform or lunate (rarely orbicular), leathery, upper margin depressed, persistent.

Gregarious on wet cliffs, rock crevices, chalky soils in caves; 600-1500 m. Guangdong, Guangxi, Guizhou, Hubei, Hunan, Sichuan, Yunnan, Zhejiang [N Vietnam].

Adiantum gravesii is very similar to A. lianxianense but differs in the plants being taller and stronger, having larger, broadly ovate or broadly obovate-triangular pinnules that are abaxially glaucous and with shorter stalks.

"Adiantum gravesii var. leveillei" (Ching ex S. K. Wu, FRPS 3(1): 181. 1990) is a nomen nudum and was not therefore validly published (Melbourne Code, Art. 38.1(a)).