21. Adiantum diaphanum Blume, Enum. Pl. Javae. 2: 215. 1828.
长尾铁线蕨 chang wei tie xian jue
Adiantum affine Willdenow; A. diaphanum var. affine (Willdenow) Alderwerelt; A. setulosum J. Smith.
Plants epilithic, 15-30 cm tall. Rhizomes erect, short, scales dark brown, lanceolate, margins denticulate. Fronds clustered; stipe castaneous, glossy, 4-20 cm, slender, adaxially grooved, base sparsely covered with same scales as rhizome, distally glabrous; lamina 1-pinnate or 2-pinnate with a few lateral pinnae nearly as large as terminal pinna, deltoid-lanceolate in outline, 6-11 × 2-3 cm; rachis, costae, and stalks castaneous, glabrous; pinnules 8-16 pairs per pinna, alternate, obliquely spreading or lower ones subhorizontally spreading; stalk less than 2 mm; blade uniform in size, dimidiate, rhombic or quadrangular, 1-1.8 × 0.5-0.9 cm, membranous, abaxially slightly glaucous and with lax, appressed, brown, unicellular needlelike setae, adaxially glossy, dark brown or deep olive-green, base asymmetrical, broadly cuneate, margin with rounded sinuses, outer margin obtuse or truncate, upper margin truncate or rounded, distal pinnules similar but slightly smaller; terminal pinnules rhombic, slightly larger; veins flabellately forked, reaching margins, visible on both surfaces. Sori 2-10 per pinnule, inserted in sinuses between lobes except those attached along veinlet but also on mesophyll between veinlets; false indusia dark brown, orbicular, leathery, upper margins deeply sinuate and with unicellular, brown, needlelike setae, persistent. Perispore indistinctly granular. 2n = 116, 232.
Wet soils or on rocks near streamsides in forests; 400-2200 m. Fujian, Guangdong, Hainan, Jiangxi, Taiwan [Indonesia, Malaysia, Vietnam; Australia, Pacific islands (New Zealand, Polynesia)].