西藏铁角蕨 xi zang tie jiao jue

Asplenium pseudofontanum Kossinsky, Bot. Mater. Gerb. Glavn. Bot. Sada R.S.F.S.R. 3: 122. 1922.

Plants (5-)13-20 cm tall. Rhizome erect, short, apex scaly; scales dark gray-brown, narrowly ovate-triangular, 3-4 × 0.5-0.6 mm. Fronds caespitose; stipe (1-)4-8 cm, base semi-shiny, castaneous to dark brown for 0.2-2 cm on adaxial side, abaxially often whole stipe brown, green toward apex, base scaly, subglabrous toward rachis; lamina lanceolate, 8-10(-15) × 1-3 cm, widest slightly above middle, gradually tapering to both ends, bipinnate to tripinnatifid at base, apex acute; pinnae 10-20(-30) pairs, subopposite to alternate, stalk 0.2-1 mm, lower pinnae reduced, sessile and more remote, middle pinnae narrowly ovate to triangular, 5-12(-25) × (2-)5-8(-12) mm, pinnatisect to pinnate, apex acute, base broadly cuneate, nearly symmetrical, basal acroscopic pinnule largest, broadly ovate, 2-4(-7) mm, close to or covering rachis, anadromous; pinnules 3-5(-7) pairs, with triangular-ovate lobes, 4-5 × 3-4 mm, base broadly cuneate and decurrent on short stalk, palmate or subpinnatilobate, apex obtuse; segments elliptic, ca. 1 mm, teeth mucronate or acute. Veins obvious, raised adaxially, 1 per segment, not reaching margin. Fronds herbaceous, pale green to grayish green when dry, lamina subglabrous, average stomatal guard cell length 30-38 µm; rachis semiterete, green, or occasionally brown at base abaxially, adaxially sulcate. Sori 1-3 per pinnule, median on acroscopic veins, linear to oval, rarely J-shaped, 1-1.5 mm; indusia whitish green or hyaline, semi-elliptic, membranous, entire, opening toward costa or costule. Spores lophate (reticulate), average exospore length 30-35 µm. Plants sexual, diploid: 2n = 72.

On limestone rocks in forests; 1500-2100 m. Xinjiang [N Afghanistan, N India, Kashmir, E Kazakhstan, E Kyrgyzstan, Nepal, N Pakistan, E Tajikistan, Turkmenistan, Uzbekistan; SW Asia (Iran)].

Asplenium fontanum consists of two morphologically slightly different but geographically widely separated, diploid subspecies with homologous chromosomes (Reichstein & Schneller, Candollea 37: 117-128. 1982; Gibby, Candollea 37: 235-242. 1982). The typical subspecies, A. fontanum subsp. fontanum, only grows on limestone rocks in C and S Europe. In Asia, it is replaced by this slightly different subspecies with somewhat wider fronds, deeply incised pinnae, and narrower segments. Its perispore is also slightly different with an outer perisporal layer with numerous small holes (fenestrate-reticulate).