二尖耳蕨 er jian er jue

Aspidium biaristatum Blume, Enum. Pl. Javae 2: 164. 1828; A. aculeatum (Linnaeus) Swartz var. biaristatum (Blume) C. B. Clarke; Polystichum aculeatum (Linnaeus) Roth ex Mertens var. biaristatum (Blume) Beddome; P. aculeatum var. durissimum Rosenstock; P. subapiciflorum Hayata.

Plants evergreen. Rhizome erect or ascending, short, densely covered with linear brown scales. Fronds up to 1 m; stipe stramineous, 50-58 cm, ca. 6 mm in diam. at base, with linear and lanceolate brown scales and larger scales; large scales denser on lower stipe, bicolorous, middle part blackish brown, margins brown, shiny, ovate-lanceolate, up to 21 × 10 mm, subentire, caudate. Lamina bipinnate, deltoid-oblong, 57-61 × 27-29 cm at middle, slightly contracted toward base, acute; rachis and costa without proliferous bulbils, densely covered with linear dark brown scales and subulate scales, subulate scale margins fimbriate. Pinnae 8-12 pairs, alternate, ascendant, shortly stalked, lanceolate, 12-14 × 2.5-2.8 cm, 1-pinnate, apices caudate-acuminate and fertile, not contracted toward base. Pinnules 14-18 pairs, alternate, shortly stalked, oblong, 1.5-2(-3) × 0.6-0.8 cm, cuneate, acute; auricles deltoid, shallowly obtusely toothed, basal acroscopic pinnules largest; abaxially with few lanceolate microscales, adaxially subglabrous; frond texture thinly leathery; venation pinnate on pinnules, lateral veins 5-8 pairs, dichotomous, distinct. Sori dark brown, 6-8 pairs per pinnule, in 1 row on each side of midrib, terminal on veinlets, abaxial pinnule surface with sori obviously concave; indusia brown, membranous, entire.

Wet places in forests; 1100-2200 m. Taiwan [Indonesia, Myanmar, Philippines, Singapore, Sri Lanka, Thailand, Vietnam].

Polystichum biaristatum has been reported as being much more widely distributed due to misidentification.

This species has laminae acute, rachis scales linear and subulate and brown, pinnae approximate, pinnules 1.5-2(-3) cm and toothed, and microscales lanceolate.