圆叶铁角蕨 yuan ye tie jiao jue

Asplenium ruta-muraria Linnaeus subsp. dolomiticum Lovis & Reichstein, Brit. Fern Gaz. 9: 143. 1964; A. deqenense Ching; A. suborbiculare Ching.

Plants 2-10(-15) cm tall. Rhizome erect to shortly creeping, scaly; scales blackish brown, narrowly triangular, occasionally with marginal glands, glands also on apex, subentire. Fronds caespitose; stipe (0.5-)2-5(-6) cm, green or grayish green to stramineous when dry, base castaneous to dark purplish or blackish brown, with numerous short (4-cellular) glandular hairs and hairlike scales, subglabrous toward rachis; lamina deltoid-triangular to ovate, (1-)2-5(-8) × 1-3(-5) cm, apex obtuse to subacute, 2-pinnate or pinnate-pinnatifid; pinnae 1-4 pairs, subopposite or alternate, basal pinnae largest, (4-)8-12 × (4-)8-10 mm, stalked, pinnae triangular, apex obtuse, imparipinnate or ternate with up to 3 lateral segments, segments often similarly divided; ultimate segments broadly flabellate to rhombic-ovate or trapeziform, (3-)4-6 × 2-5 mm, base broadly cuneate and decurrent on costa, margin irregularly dentate, apex obtuse. Veins obscure, flabellately anadromous, and almost parallel. Fronds subleathery, grayish green when dry; rachis and costa green, with (partly) deciduous glandular hairs, subglabrous when old, adaxially sulcate, when dry often flat. Sori 5-12 per pinna, median on subtending vein, confluent at maturity, subelliptic to linear, 1-5 mm; indusia gray-glaucous to brown, linear, thinly membranous, margin with long hairs, opening toward major veins or costa, concealed by sporangia at maturity. Perispore lophate (costate-cristate), average exospore length 35-40 µm. Plants sexual, diploid: 2n = 72.

In rock crevices (often dolomite); 1500-3300 m. Hebei, Sichuan, Xizang, Yunnan [Afghanistan, Mongolia, Russia (E Siberia); SW Asia (Iran, Turkey), S Europe].

Contrary to previous reports, new and more extensive research in S Europe has shown that there are no gross morphological differences between Asplenium dolomiticum and A. ruta-muraria (see below). Asplenium deqenense and A. suborbiculare, both with an average exospore length of 39-40 µm, are considered juvenile, depauperate forms of A. dolomiticum. Small juvenile forms with simple or ternate fronds are not rare in populations of both A. ruta-muraria and A. dolomiticum.