泸山铁角蕨 lu shan tie jiao jue

Plants 3-15 cm tall. Rhizome erect, scaly; scales dark brown, narrowly triangular, margin fimbriate at base. Fronds caespitose; stipe purplish black to castaneous, semi-shiny, 0.5-4 cm, adaxially sulcate, with dark brown narrowly triangular scales mixed with filiform scales; lamina linear or linear-lanceolate, 3-15 × 0.5-2.5 cm, attenuate to both ends, apex pinnatipartite or long flagelliform with terminal budlet, 1-pinnate to 2-pinnatifid; pinnae 10-20 pairs, pinnae sessile or shortly stalked, basal pinnae usually smaller and flabellate, middle pinnae largest, distinctly separated from each other, linear-elliptic, (2-)5-10(-15) × 1.5-5(-7) mm, base almost symmetrical to asymmetrical, acroscopic side truncate, basiscopic side broadly cuneate, pinnatipartite, apex obtuse and with 1 gemma in apical sinus; segments 1-4 pairs, apex obtuse but with 2 or 3 teeth, basal acroscopic segment not much enlarged. Veins not prominent, anadromously forking, not reaching margin. Fronds herbaceous, green, lamina with uniseriate gland-tipped hairs or subglabrous, average guard cell length 34-39 µm; rachis with purplish brown to castaneous color extending from basal part up to 1/2-2/3 its length on abaxial side, apical part green or stramineous when dry, with purplish black hairlike scales, adaxially green or stramineous, flat or slightly sulcate, green. Sori usually 1 per segment, often confluent at maturity, subelliptic, 0.3-1 mm, basal to submedial on subtending veinlets, close to costa; indusia grayish green to grayish brown, subelliptic, membranous, repand to entire, mainly opening toward costa. Spores with lophate (costate-cristate) perispore, average exospore length 24-28 µm. Plants sexual, diploid: 2n = 72.

In rock (limestone) crevices in forests; 1100-2800 m. Sichuan, Yunnan [Nepal, Vietnam].

Asplenium lushanense is the diploid ancestor of autotetraploid A. exiguum (Viane & Reichstein, Pterid. New Millennium, 91-94. 2003; Wang, Acta Bot. Sin. 45: 1-14. 2003), see below.