24. Asplenium tripteropus Nakai, Bot. Mag. (Tokyo). 44: 9. 1930.
三翅铁角蕨 san chi tie jiao jue
Asplenium anceps Hooker & Greville var. proliferum Nakai; A. trialatum C. Christensen; ?A. trichomanes Linnaeus var. centrochinense Christ.
Plants 15-30 cm tall. Rhizome erect, short, apex scaly; scales narrowly triangular, 3.5(-5) × ca. 0.5 mm, with brown central stripe and paler clathrate borders, entire. Fronds caespitose; stipe shiny brown to black, 3-5 cm, stout, base terete, densely scaly, upward subglabrous and becoming trigonous and then triangular, abaxially carinate to winged and adaxially flat to sulcate with a brown membranous wing along each lateral side, stipe and rachis usually persistent after shedding of pinnae; lamina linear, 12-28 × 1-2.5 cm, attenuate to both ends, 1-pinnate; pinnae 20-35 pairs, (sub)opposite to alternate, usually at right angles to rachis, sessile, middle pinnae oblong to rectangular, 5-13 × 2-7 cm, base asymmetrical, acroscopic side truncate, sometimes auriculate, parallel with or covering rachis, basiscopic side narrowly cuneate, margin crenate, apex obtuse; basal pairs of pinnae gradually reduced, flabelliform. Veins pinnate, costa obscure, veins 1-forked. Fronds papery, green or brownish green when dry; rachis stout, shiny dark brown to black, subglabrous, triangular, abaxially winged, adaxially sulcate with 2 entire, lateral, brown membranous wings, often gemmiferous near apex, with 1 or 2(or 3) scaly axillary buds. Sori 3-6(-11) per pinna, linear, 1-2 mm; indusium grayish green, semi-elliptic, membranous, entire, opening toward costa.
On wet rocks or in acidic soil in forests; 400-2500 m. Anhui, Fujian, Gansu, Guizhou, Henan, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Taiwan, Yunnan, Zhejiang [Japan, Korea, Myanmar].
As presently circumscribed, Asplenium tripteropus is an aggregate of a diploid and a tetraploid species (2n = 72 or 144) both in China and in Japan (Mitui, J. Jap. Bot. 40: 117-124. 1965; Tatuno & Kawakami, Bot. Mag. (Tokyo) 82: 436-444. 1969; Wang in K. H. Shing & K. U. Kramer, Proc. Int. Symp. Syst. Pterid. 133-134. 1989). Further studies will need to characterize and distinguish them, not only from each other but also from the non-gemmiferous, Macaronesian A. anceps.
This species is similar in outline to Asplenium trichomanes, but the plants can easily be distinguished by their triangular and winged stipe and rachis and by the presence of a bud on some fronds.