扁柄巢蕨 bian bing chao jue

Asplenium longistipes (Ching ex S. H. Wu) Viane; Neottopteris humbertii (Tardieu) Tagawa; N. longistipes Ching ex S. H. Wu.

Plants up to 30 cm tall. Rhizome erect, short, scaly; scales brown, triangular-ovate, margins sparsely ciliate. Fronds caespitose; stipe greenish stramineous, 4-8 cm, soft, without wide wing on lateral side, base with dark brown scales or subglabrous; lamina spatulate, 18-22 × 3.5-5 cm, lower part decurrent on stipe and cuneate, margin entire, apex cuspidate to shortly caudate. Midrib (rachis) almost flat to slightly semiterete, stramineous, abaxially occasionally with small brown scales; veins obscure adaxially, faintly visible abaxially, simple or forked. Fronds leathery, after drying grayish green, subglabrous. Sori linear, 1-1.5(-2.5) cm, on acroscopic veinlets, occupying 1/2-2/3 of subtending vein; indusia grayish yellow, linear, thickly membranous, entire, persistent. Spores with lophate areolate-fenestrate perispore. Plants sexual hexaploid: 2n = 216.

Epilithic on limestone rocks in wet forests; 800-900 m. Guangxi, Hainan, SE Yunnan [Laos, Thailand, Vietnam].

Specimens of Asplenium humbertii from Hainan have longer sori than the type, collected in Vietnam. The species is rather similar to A. grevillei Wallich ex Hooker & Greville from India and Thailand, which differs by its smaller scales, distinctly keeled midrib, and areolate-fenestrate perispore (Wei & Dong, Nordic J. Bot. 30: 90-103. 2012). However, the relationship between A. grevillei, A. humbertii, and A. antrophyoides requires further study.