岭南铁角蕨 ling nan tie jiao jue

Asplenium tenerum G. Forster var. stenophyllum Bonaparte ["stenophilla"].

Plants 15-35 cm tall. Rhizome erect, short, apex scaly; scales dark brown to black with pale brown narrow edge, triangular to ovate, margin glandular denticulate or fimbriate. Fronds caespitose; stipe 3-8 cm, semiterete, fleshy, adaxially sulcate but with prominent median supravascular ridge, green or stramineous when dry, base abaxially often dull brown, with dark brown to black triangular scales with filiform apex and smaller hastate-stellate scales; lamina lanceolate, 13-25 × 2-5 cm, attenuate to both ends, apex acute-acuminate, bipinnatisect; pinnae 17-28 pairs, subopposite or alternate, stalk ca. 1 mm, at base reduced and often triangular, middle pinnae oblong-elliptic, slightly falcate, 1.2-2.5 × 0.6-1.2 cm, base symmetrical, truncate, pinnatisect, apex obtuse; segments 5-9 pairs, alternate, anadromous, linear-oblong, 2-4 × 1-1.5 mm, apex obtuse, base confluent with costa and forming costal wing, entire, basal acroscopic segment larger and 2-5-fid. Costa distinct and raised adaxially, obscure abaxially, venation anadromously pinnate, 1 vein per segment, not reaching margin. Frond usually subfleshy, green to stramineous when dry, with dark brown stellate-hastate scales with filiform tail on abaxial surface; rachis sulcate but with prominent supravascular ridge on adaxial side, green or stramineous when dry, fleshy. Sori 1 per segment, on acroscopic side of subtending vein, linear, 2-2.5 mm; indusia whitish to gray-stramineous, oval-linear, membranous, entire, opening toward costa and margin, persistent. Spores with medium to dark brown lophate (costate-cristate) perispore. Plants decaploid: 2n = 360.

On limestone rocks in open forests; 300-800 m. Guangdong, Guangxi, S Guizhou, Hainan, SE Yunnan [Vietnam].

Asplenium sampsonii is similar to A. thunbergii Kunze (=A. belangeri (Bory) Kunze (1848), not Bory (1833)) from Malaysia and Indonesia, but it is smaller, not gemmiferous on the rachis; the lower pinnae are reduced; and the perispore is different. The distinction between A. sampsonii and A. thunbergii in Chinese floras (e.g., S. H. Wu, FRPS 4(2): 124. 1999; T. L. Wu et al., Fl. Guangdong 7: 190, 203-204. 2006) is based largely on size differences. Manton (in Holttum, Revis. Fl. Malaya 2: 623-627. 1954) found that plants from Malaysia are tetraploid, but since specimens from Hainan and Guangxi are decaploid, we are confident that they are different from true A. thunbergii, which probably does not occur in China. Plants of A. tenerum with bipinnatifid fronds can be similar to this species.