江南铁角蕨 jiang nan tie jiao jue

Asplenium loxogrammoides Christ.

Plants 20-40 cm tall. Rhizome erect, short, apex scaly; scales dark brown, narrowly triangular, entire. Fronds simple, clustered; stipe grayish stramineous, 2-4 cm, with scales; lamina lanceolate, 15-30(-36) × 2.5-3.5(-4) cm, base decurrent on stipe, margin pale, ± entire to repand or sinuate, apex acuminate to subcaudate. Midrib (rachis) distinctly raised and semiterete on both surfaces in basal half of lamina, with dark brown to black filiform paleasters (rudimentary scales), brownish; veins obscure, 1-forked. Fronds herbaceous, dark green to brown when dry, subglabrous or with small stellate scales. Sori linear, 1.4-2.1(-2.5) cm, often starting close to midrib or more medial, at an angle of (20°-)30°-40°, on acroscopic veinlets; indusia yellowish brown to deep brown, linear, thickly membranous, margin composed of thin-walled hyaline cells, entire to repand, opening toward midrib, persistent. Spores with alate perispore.

On rocks by streamsides in forests; 500-1000 m. Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangxi, Sichuan, Taiwan, Yunnan [Vietnam].

Asplenium holosorum is similar to A. ensiforme but generally grows at lower elevations. Its fronds are more herbaceous and their midrib (rachis) is flat near the apex but raised adaxially in the lower half of the frond and not sulcate. Both species have a similar epidermis structure with cryptopolocytic to basipolocytic (also called anomocytic, staurocytic, or cyclocytic) stomata. In both taxa, the outer free margin of the indusium consists of translucent cells with very thin walls, but this marginal rim is narrow (ca. 2 cell layers) in A. holosorum, but more elaborate and dentate-fimbriate in A. ensiforme.

No chromosome counts seem to be available, but our recent FCM results suggest this taxon is probably hexaploid.