天坑耳蕨 tian keng er jue

Plants summer-green, 7-22 cm tall. Rhizome ascending, ca. 1 cm, sparsely or densely covered with scales; scales brown, linear, ca. 0.1 mm; roots dark brown when dry, up to 12 cm, ca. 0.3 mm in diam. Fronds 5-10 per rhizome; stipe green, 3-9 cm, 0.3-0.9 mm in diam. at middle; basal stipe scales brown, dull, lanceolate, 1.2-3.5 × 0.1-0.8 mm, papery or membranous, composed of multiple cell layers, margins minutely ciliate, apices long caudate; distal stipe scales brown, dull, lanceolate, 1-2.8 × 0.1-0.3 mm, varying in size, composed of 1 or 2 cell layers, membranous, margins long ciliate, apices long caudate. Lamina 1-pinnate, lanceolate, slightly contracted toward base, 8-14 × 1.6-2.4 cm at middle, broadest part 1.8-2.7 cm wide near base, apex truncate; rachis 0.2-0.5 mm in diam. at middle, with 2 proliferous bulbils, one each at both base and apex of rachis, sometimes with only 1 bulbil at either base or apex, rarely without bulbils; scales of rachis similar to distal stipe scales but smaller, brown, dull, varying in size, papery, margins minutely ciliate, apices caudate. Pinnae 13-22 pairs, not overlapping, pointing slightly upward, basal two pairs 0.5-1.2 cm apart, alternate but nearly opposite at frond base, deltoid in lower part of lamina, oblong in upper part of lamina; middle pinnae 0.9-1.2 × 0.5-0.7 cm; largest pinnae in lower half of lamina, shortly stalked, asymmetrical at base, bipinnatifid. Lobes 2 or 3 pairs per pinna, alternate, elliptic or oblong, acute, basalmost pairs of lobes free or almost free; both surfaces scaly; microscales on both surfaces subulate without dilated base (narrow-type microscales), 0.9-2.25 mm, base ca. 0.1 mm wide, with few tortuous cilia on basal margin; frond texture papery; venation pinnate; midrib slightly raised abaxially, flat adaxially. Sori terminal on veinlets, entire abaxial lamina fertile, 2-5 sori per pinna, close to midrib, center of sorus 1.2-1.6 mm distant from pinna margin; indusia brown, 1-1.2(-1.5) mm in diam., membranous, erose.

● Wet basic soil among limestone rubble, limestone cliffs at entrances of caves at bottom of sinkholes; ca. 2500 m. NW Guizhou (Hezhang).

Polystichum tiankengicola can have two proliferous bulbils on each end of the rachis, distinguishing it from all other species in the genus.