51. Polystichum costularisorum Ching ex W. M. Chu & Z. R. He, Fl. Reipubl. Popularis Sin. 5(2): 224. 2001.
轴果耳蕨 zhou guo er jue
Plants evergreen. Rhizome ascending, short. Fronds ca. 20 cm; stipe stramineous, slender, ca. 9 cm, less than 1 mm in diam. at base, whole stipe scaly; scales yellowish brown, lanceolate, thin; basal stipe scales sparse, broadly ovate, with few long teeth or subentire. Lamina 1-pinnate, narrowly elliptic-lanceolate, ca. 13 × 2.5 cm, apex pinnatifid-acuminate; rachis stramineous, without proliferous bulbils, sparsely covered with remnant scales similar to stipe scales. Pinnae ca. 10 pairs, oblong-ovate, sessile, bases asymmetrical, margins pinnatifid to pinnatilobate, apices acute; acroscopic base auriculate, basiscopic margins oblique, at right angles to rachis or slightly angled basiscopically; middle pinnae largest, up to 1.5 cm × 7 mm; basal pinnae contracted and rhombic, ca. 5 mm long and wide, lobes and teeth acute at apex; frond texture papery; venation slightly visible, pinnate on pinnae, veinlets often simple, rarely forked. Sori abaxial on lower part or base of veinlets, 2-8 per pinna, often close to midrib when mature; indusia present, light brown with dark brown centers, erose.
● Wet rocks; ca. 2500 m. W Sichuan (Luding).
Polystichum costularisorum is similar to P. thomsonii, but its stipe is nearly as long as its rachis and its lamina has only 10-16 pairs of pinnae, which are pinnatilobate to pinnatifid.