吞天井耳蕨 tun tian jing er jue

Plants evergreen. Rhizome ascending, 0.5-1 cm; scales brown, linear, 0.2-3.6 mm; roots dark brown when dry, up to 9 cm, ca. 0.6 mm in diam., sparsely or densely covered with scales. Fronds 4-7 per rhizome, 5-14 cm; stipe green, 2-6 cm, 0.6-1.2 mm in diam. at middle; basal stipe scales ovate-lanceolate, 3.6-4.5 × 1.1-2.3 mm, papery, abaxially brown and dull, adaxially flat, dark brown and shiny, margins ciliate or erose, apices acuminate or caudate; distal stipe scales brown, ovate-lanceolate, 2.7-3.7 × 1.1-2.1 mm, varying in size, membranous, composed of 1 layer of cells, margins regularly ciliate or with outgrowths, apices caudate, matte. Lamina 1-pinnate, shiny adaxially, lanceolate, 3.5-9.5 × 1.2-2.6 cm at middle, 1.3-2.7 cm wide and broadest at base, apex acute; rachis 0.7-1.2 mm in diam. at middle, without proliferous bulbils; scales of rachis similar to distal stipe scales but smaller, varying in size, margins regularly ciliate, apices caudate, matte. Pinnae 6-14 pairs, remote, strongly reflexed toward lamina base, basal two pairs 0.7-1.5 cm apart, alternate, oblong, middle pinnae 7.5-12 × 3.5-5.5 mm, basal pinnae slightly larger, shortly stalked, acroscopic base slightly auriculate, basiscopic base cuneate, forming 30°-90° angle with rachis, apices acute, margins crenate or subentire, without spinules; abaxially scaly, adaxially glabrous; microscales on abaxial surface subulate with dilated base (broad-type microscales), 0.5-1.1 mm, base 0.13-0.26 mm wide, with few tortuous outgrowths on margin of base; frond texture thinly leathery; venation pinnate; midrib slightly raised abaxially, flat adaxially; lateral veins free, 4 or 5 pairs from midrib per pinna, each lateral vein further dichotomous, indistinct on both surfaces. Sori terminal on veins of pinnae, 5-9 (1-3 below midrib, 4-6 above midrib) per fertile pinna, located approximately at middle between midrib and pinna margin and 0.9-1.6 mm distant from pinna margin; all pinnae on fertile lamina fertile; indusia brown, 0.8-1.2 mm in diam., erose. Spores subglobose in polar view, elliptic in equatorial view, ca. 32.5(28-37) × 43.5(36-48) × 34.2(31-38) µm (polar axis × long equatorial axis × short equatorial axis, respectively); perispore sculpturing cristate with numerous spinules ca. 0.5 µm.

● Limestone walls inside karst sinkholes; ca. 1700 m. NW Guizhou (Bijie).

Polystichum puteicola is most similar to P. obliquum in stature, pinna shape, and pinna size, but P. puteicola has the lamina widest at the base, stipe scales blackish brown adaxially, rachis scales up to 3.6 × 0.8 mm, pinnae oblong, dark green, nearly leathery, shiny adaxially, and slightly repand-serrate or subentire, and microscales brown and up to 2 × 0.5 mm. In contrast, P. obliquum has a narrowly oblanceolate lamina with the basal pair of pinnae contracted, stipe scales brown adaxially, rachis scales up to 2.3 × 0.5 mm, pinnae rhombic-ovate or rarely oblong, green, papery, dull adaxially, and serrulate, and microscales brownish and 0.5-0.8 × 0.2-0.3 mm.

Polystichum puteicola is also similar to P. paradeltodon in stature and pinna size but differs in having fronds thicker and dark green and pinnae oblong, ± reflexed, with basiscopic base attached at 30°-90° angle with rachis (vs. fronds thinner, green or yellowish green, and pinnae falcate-triangular, attached at 100°-110° angle with rachis).