西疆铁角蕨 xi jiang tie jiao jue

Plants (3.5-)6-15(-25) cm tall. Rhizome erect, short, apex scaly; scales brown to dark brown, triangular to narrowly triangular, (2-)2.2-3.5(-4.5) × 0.4-0.7 mm, fimbriate or entire. Fronds caespitose; stipe green (small fronds) but base dark brown, color occasionally extending into rachis, (1-)2-6(-9) cm, with small dark brown, often linear scales and uniseriate hairs, subglabrous when old, adaxially sulcate; lamina narrowly oblong to ovate, (2.3-)5-10(-20) × (0.7-)1-2.5(-4) cm, base truncate-cuneate, bipinnate at base, pinnate-pinnatisect(-pinnatifid) in upper part, apex acute-acuminate to caudate; pinnae 7-13 pairs, alternate or opposite, stalk ca. 1 mm, lower pinnae slightly reduced, lowest pair 0.8-1.8 cm from next pair, more distal pinnae closer but usually not overlapping, median and upper pinnae often at an angle of 45°-75° to rachis, largest pinnae triangular-ovate, 10-20 × 5-10(-12) mm, base asymmetrical, acroscopic side truncate, basiscopic side cuneate, basal acroscopic pinnule largest, often shortly (ca. 0.5 mm) stipitate and nearly parallel to rachis, fan-shaped or ovate to triangular-ovate, margin serrate to crenate with acute to mucronate teeth, apex obtuse; basiscopic pinnules often adnate and directed outward, almost perpendicular to rachis. Fronds herbaceous, green to gray-green or brown when dried, rachis green or occasionally with castaneous base (abaxially), adaxially sulcate, with small, dark brown, linear scales, lamina with 3- or 4-celled uniseriate gland-tipped hairs, epidermis cells with sinuous pseudomamillate anticlinal walls, average guard cell length 45-50 µm. Sori 1-3(or 4) per pinnule, median on acroscopic veinlets, often confluent at maturity, oval-linear, 1.4-2.4(-3) mm; indusia whitish to pale brown, oval-linear, membranous, entire to repand, opening toward major veins or costa. Spores with lophate (costate-cristate) perispore, average exospore length 32-36 µm. Plants sexual, allotetraploid: 2n = 144.

On rocks in forests; 2100-3300 m. Xizang, Yunnan [India, Nepal, Pakistan].

Asplenium kukkonenii is most similar to A. tenuicaule and A. varians. Crossing experiments and micromorphology have shown that A. tenuicaule is one of its ancestors (Viane & Reichstein, Pterid. New Millennium, 73-105. 2003). The second ancestor of A. kukkonenii is still unknown. The fact that A. kukkonenii and A. varians share a genome explains why these taxa are difficult to differentiate from each other. The lamina of A. kukkonenii is usually slightly narrower and more acuminate (occasionally even caudate) at the apex. The mean length of the rhizome scales is usually less than 3.5 mm in A. kukkonenii and more than 3.5 mm in A. varians. Reliable differentiation is also possible by examination of epidermal cells, which are thickened or pseudomamillate in their sinuses in A. kukkonenii, but not so in A. varians. In herbaria, A. kukkonenii is often identified as A. varians or as A. fontanum and was included in A. varians by, e.g., Beddome (Handb. Ferns Brit. India, 158. 1883), Hope (J. Bombay Nat. Hist. Soc. 13: 667. 1901), Stewart (Biologia 3: 133-164. 1957), Stewart in Nasir & Ali (Fl. W. Pakistan, 18. 1972), Nakaike and Malik Cryptog. Fl. Pakistan) 1: 270. 1992; Cryptog. Fl. Pakistan 2: 332. 1993), and G. F. Zhang (Fl. Yunnan. 20: 673. 2006).