宪需耳蕨 xian xu er jue

Plants ?evergreen. Rhizome erect or slightly prostrate, 0.5-2 cm, 2-3 mm in diam., up to 1.5 cm in diam. with base of remnant old stipes; scales dull brown, linear-lanceolate, ca. 3 × 0.8 mm, subentire; roots up to 10 cm, 3-4 mm in diam. Fronds 12-16 cm; stipe stramineous, 1.5-4.5 cm, 1-2 mm in diam. at middle; scales on basal stipe brown, narrowly deltoid-lanceolate, 3-4 × 0.3-1.2 mm, thinly papery, margins at base with outgrowths; outgrowths hairlike, tortuous and soft; margins upward sparsely fimbriate or subentire, apices filiform; scales on distal stipe similar but narrower, brown, mostly linear-lanceolate, up to 3 × 0.5 mm, apices filiform. Lamina 1-pinnate-pinnatifid, yellowish green adaxially, slightly paler abaxially, lanceolate, 5.5-12.5 × 1.5-2.5 cm, slightly narrower at base, acuminate toward apex; rachis 0.5-1.2 mm in diam. at middle, apex with a small proliferous bulbil, without flagelliform prolongation. Pinnae 18-22 pairs, 0.5-1.5 × 0.3-0.6(-0.8) cm, shortly stalked, alternate, lower pairs deltoid-lanceolate, attached nearly at right angles to rachis, upper pairs shorter and rhombic-lanceolate, spreading to slightly ascending, acroscopic base auriculate, basiscopic base cuneate, apices acute and terminating in a mucronate spine, several pairs of pinnae below middle of lamina deeply pinnatifid with their proximal pair of lobes nearly free, pairs above middle serrate with a mucronate tip at tooth apex and basal acroscopic auricle deltoid; lobes obliquely oblong to obovate, entire, mucronate; frond texture papery; abaxially moderately clothed with scattered microscales, adaxially with occasional articulate hairs especially along midrib; microscales brown, linear-subulate, up to 2.5 mm, usually with few tortuous hairlike outgrowths at margin of their broader base; frond texture thinly papery; venation pinnate, obvious abaxially, lateral veins free, 1-2 times forked. Sori terminal on distal branchlets of forked veinlets, 0.5-2.5 mm apart (when young), (1-)3-5(or 6) in 1 row on each side of midrib, submarginal; indusia irregularly lacerate, membranous, glossy brown later, adjacent ones often overlapping by 0.5-1.5 mm and extending over pinna margin when mature.

● Shaded wet limestone walls at edges of small NE-facing down-ward sloping karst caves; ca. 1800 m. Chongqing (Wuxi), Hunan (Shimen).

Polystichum kungianum has a similar stature and lacerate indusia to P. erosum, but the pinnae below middle of the lamina of the former are profoundly pinnatifid with the proximal pair of lobes nearly free from the other parts. Basal and adjacent pairs of pinnae of P. kungianum are attached nearly at right angles to rachis, whereas they are usually ± reflexed in P. erosum. Most importantly, P. kungianum has deltoid-lanceolate pinnae and a rather small terminal bulbil borne directly on the apex of the rachis which never elongates, while P. erosum has a much larger terminal bulbil on the rachis which usually elongates between the terminal bulbil and the uppermost part.