离脉柳叶耳蕨 li mai liu ye er jue

Cyrtogonellum tenuius Ching, Bull. Fan Mem. Inst. Biol., Bot. 8: 329. 1938 ["tenuium"]; C. caducum Ching; C. falcilobum Ching ex Y. T. Hsieh; C. salicifolium Ching ex Y. T. Hsieh.

Plants evergreen. Rhizome erect or ascending, together with basal stipe densely scaly; scales dark brown, ovate-lanceolate, thickly membranous, toothed, acuminate. Fronds 30-70(-100) cm; stipe stramineous, 15-25(-46) cm, 1.5-2.5 mm in diam. at middle; distal stipe scales smaller, brown, subulate, membranous, margins ciliate, apices filiform. Lamina 1-pinnate, grayish green when dry, adaxially shiny, broadly lanceolate, 15-30(-54) × 6-10 cm at middle, base truncate, not or only basalmost pairs contracted toward base, apex pinnatifid-acuminate; rachis stramineous, without proliferous bulbils, abaxially sparsely scaly; scales similar to distal stipe scales but smaller, brown, subulate, margins ciliate, apices filiform. Pinnae 13-24 pairs, alternate, approximate, attached at right angles to rachis or angled slightly acroscopically or basiscopically, shortly stalked, lanceolate or rarely falcate-lanceolate, basal pairs 3.5-7 × 0.8-1.8 cm, bases nearly symmetrical, acroscopic base hardly auriculate, proximal acroscopic margins of pinnae slightly curved and forming a 0°-30° angle with rachis, acroscopic margins truncate or very slightly recurved, subentire or shallowly incised-toothed, basal basiscopic margins cuneate, forming a ± 45° angle with rachis, entire, distal basiscopic margins slightly curved upward, shallowly incised-toothed, apices acuminate; adaxially glabrous, abaxially sparsely scaly; microscales light brown, filiform; frond texture thickly papery to thinly leathery; venation pinnate, distinct abaxially, indistinct adaxially; lateral veins 3- or 4-forked, not reaching pinna margin. Sori in 1 row on each side of midrib, terminal on veinlets, medial, basalmost pinnae often sterile; indusia present, brown, membranous, entire, evanescent. 2n = 123.

Limestone crevices in forests; 300-1700 m. Chongqing, Guangxi, Guizhou, Hunan, Sichuan, Yunnan [N Vietnam].

The original epithet "tenuium" is a correctable error of "tenuius."

Cyrtogonellum caducum and C. tenuius were published in the same paper and thus have the same priority. When the species is transferred to Polystichum, the epithet "caducum" is blocked by Polystichum caducum Diels (Nat. Pflanzenfam. 1(4). 194. 1899).