26. Asplenium quadrivalens (D. E. Meyer) Landolt, Fl. Indicativa. 268. 2010.
四倍体铁角蕨 si bei ti tie jiao jue
Asplenium trichomanes Linnaeus subsp. quadrivalens D. E. Meyer, Ber. Deutsch. Bot. Ges. 74: 456. 1962; A. melanolepis Colenso, p.p. (1888), not Franchet & Savatier (1879).
Plants 10-30 cm tall. Rhizome erect, short, scaly; scales narrowly triangular, 3.5(-5) × ca. 0.5 mm, with opaque dark brown to black central stripe and paler narrow clathrate borders, entire. Fronds caespitose; stipe shiny castaneous or dark red-brown to black, 2-8 cm, base scaly, upward subglabrous, abaxially semiterete but adaxially sulcate, with brown, membranous and subentire narrow wings, texture papery, stipe and rachis usually not very long persistent after shedding of pinnae; lamina linear, 10-25 × 0.9-1.6 cm, base slightly reduced, 1-pinnate, apex acute and 2-5 mm wide; pinnae 20-30 pairs, usually at right angles to rachis, sessile, middle pinnae oblong to rectangular, 4-6(-12) × 2-4(-5) mm, base asymmetrical, truncate, acroscopic side occasionally auriculate, margin crenate, apex obtuse; lower pinnae gradually reduced, flabellate or triangular. Veins pinnate, costa obscure, veins oblique, simple or up to 2-forked, basal acroscopic vein usually 2-forked. Fronds papery, green or brown when dry, stomatal guard cells 41-48 µm; rachis castaneous, shiny, subglabrous, abaxially terete, adaxially grooved and with a relatively high lateral brown membranous wing. Sori 4-8 per pinna, oval to linear, 1-3.5 mm, usually on acroscopic vein; indusium white or brown after drying, oval to linear, membranous, free margin repand to entire, opening toward costa, persistent. Spores with lophate (costate) perispore, average exospore length 32-37 µm. Plants sexual tetraploid: 2n = 144.
In crevices of various kinds of rocks (often calcareous), in open or half-shaded situations; 400-3400 m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [worldwide in all temperate zones, in tropics on high mountains].
Tetraploid Asplenium quadrivalens has a broader ecological amplitude, i.e., it is not limited to non-calcareous substrates and has a wider range than A. trichomanes.
"Asplenium lovisii" (Rothmaler, Wiss. Z. Ernst-Moritz-Arndt-Univ. Greifswald, Math.-Naturwiss. Reihe 14(1/2): 77. 1965) belongs here but was not validly published because no type was indicated (Melbourne Code, Art. 40.1); its "type" was a cultivated plant and not a specimen as required by Art. 8.4. If the proposal to conserve the name A. trichomanes with a conserved type, based on a diploid plant according to its traditional ("2x") use and in compliance with Art. 57.1, is not accepted then the name for the current tetraploid species will have to change to A. trichomanes.
Asplenium ×heufleri Reichardt (the tetraploid sterile hybrid between A. quadrivalens and A. septentrionale) was recently found in Xinjiang. The authors have not seen any specimens of A. ×alternifolium Wulfen (the triploid sterile hybrid between A. trichomanes and A. septentrionale).