雅安耳蕨 ya an er jue

Plants evergreen, 8-15 cm tall. Rhizome ascending, short, 0.5-1 cm, 2-3 mm in diam.; scales light brown, ovate-lanceolate, 0.4-3.6 mm, papery; roots dark brown when dry, up to 10 cm, ca. 0.6 mm in diam., sparsely or densely covered with scales. Fronds 5-11 per rhizome; stipe green, 1.5-3 cm, 0.5-1.2 mm in diam. at middle; basal stipe scales brown at middle and light brown on margin, dull, ovate-lanceolate, 2.7-3.4 × 0.8-1.1 mm, varying in size, thinly papery at middle, membranous on margin, margins subentire or ciliate, apices acuminate or caudate; distal stipe scales similar but narrower and shorter toward stipe apex, brown, dull, lanceolate or ovate-lanceolate, membranous, margins ciliate, apices caudate. Lamina 1-pinnate, shiny adaxially, lanceolate, 6-12 × 1.4-1.8 cm at middle, 1.6-2 cm wide at widest, contracted toward base, acute; rachis 0.7-1.2 mm in diam. at middle, without proliferous bulbils; rachis scales light brown, dull, narrowly ovate to lanceolate, 1.5-3.2 mm, base 0.3-1 mm wide, papery, margins slightly ciliate, apices caudate. Pinnae 10-26 pairs, approximate, angled acroscopically, basal two pairs 0.5-1.3 cm apart, alternate, yellowish green, oblong; largest pinnae 8.2-10.1 × 4.5-5.1 mm and located around lamina middle, shortly stalked, stalks ca. 1.5 mm, acroscopic base auriculate, basiscopic base truncate and often forming a 90°-120° angle with rachis, acroscopic margin repand-serrate and without aristate spinules, apices obtuse; abaxially scaly, adaxially glabrous; microscales on abaxial surface subulate without dilated base (narrow-type microscales), 0.3-0.9 mm, base 0.12-0.24 mm wide, ciliate on margin; frond texture leathery; venation pinnate; midrib slightly raised abaxially, flat but obviously visible adaxially; lateral veins free, 3 or 4 pairs from midrib per pinna, nearly opposite, each lateral vein further dichotomous, distinct on both surfaces. Sori terminal on veins of pinnae, (1 or)2-5 per fertile pinna, close to and ca. 0.9 mm distant from pinna margin; all pinnae on fertile lamina fertile; indusia brown, 0.7-1.1 mm in diam., erose.

● Shallow acidic soils on wet shaded sandstone cliffs; 900-1100 m. Sichuan (Hongya, Ya’an).

Polystichum yaanense is unique in the whole P. subg. Haplopolystichum in having yellowish green fronds with a thin but hard texture and adaxially visible veins. Polystichum yaanense grows in acidic soils, which also distinguishes it from most species in the subgenus. Its ovate-lanceolate rachis scales are shared only by P. loratum in the subgenus.