变异铁角蕨 bian yi tie jiao jue

Asplenium lankongense Ching; A. paucijugum Ching (1985), not F. Ballard (1935).

Plants (4-)8-20(-35) cm tall. Rhizome erect, short, apex scaly; scales dark brown to black, narrowly triangular, (1.5-)3-4.2(-5) × 0.5-1 mm, fimbriate at base or subentire. Fronds caespitose; stipe semiterete, (0.5-)2-7(-12) cm, adaxially green and sulcate, abaxially shiny castaneous, brown color occasionally extending to rachis, with small dark brown, very narrow scales and uniseriate hairs, subglabrous when old; lamina triangular-ovate, (3-)6-13(-25) × (1-)2-4(-8) cm, base slightly reduced, bipinnate, apex acute-acuminate; pinnae (5-)8-12(-18) pairs, lower pinnae (sub)opposite, upper alternate, stalk ca. 1 mm, largest pinnae triangular-ovate, 8-17(-30) × (3-)6-10(-15) mm, base asymmetrical, acroscopically semicordate-truncate, basiscopic side cuneate, 1-pinnate, apex obtuse; pinnules 2 or 3 pairs, alternate, anadromous, basal acroscopic pinnule largest, fan-shaped to orbicular-obovate, 3.5-5.5 × 2.5-4(-6) mm, base cuneate, sessile to almost free, lateral side entire, apex serrate and obtuse; other segments smaller, usually adnate to costa. Veins not obvious, slightly raised adaxially when dry, anadromously forking, not reaching margin. Frond herbaceous, green or grayish green when dry; lamina with 3- or 4-celled uniseriate gland-tipped hairs, average guard cell length 46-52 µm; rachis semiterete, grayish green and sulcate adaxially, occasionally brown at base abaxially, subglabrous. Sori 2-4 per pinnule, submedian to median on subtending vein, often confluent at maturity, oval to linear, (1-)1.5-3(-4.5) mm; indusia gray, linear, membranous, repand to entire, opening toward costule or costa, persistent. Spores with cristate-alate perispore, average exospore length 31-35 µm. Plants sexual allotetraploid: 2n = 144.

On wet rocks or cliffs in forests, or on buildings and walls; 500-4200 m. Chongqing, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Shaanxi, Sichuan, Xizang, Yunnan [Bhutan, India, Nepal, Vietnam; S Africa].

Sleep and Reichstein (Candollea 39: 675-691. 1984), following Morton (Contr. U.S. Natl. Herb. 38: 215-281. 1973), discussed the problem of the application of the name Asplenium laciniatum D. Don (Prodr. Fl. Nepal. 8. 1825). That name applies to a taxon closely related to A. varians, but its type is merely a depauperate single frond with a few spores and is not adequate for the precise application of the name. Moore (Index Fil. 139. 1857) and Hooker (Sp. Fil. 3: 164-165. 1860) misapplied the name A. laciniatum to another Himalayan fern species not related to A. varians, i.e., A. gueinzianum. Most later authors then followed that misapplied concept of A. laciniatum. Viane and Reichstein (Taxon 35: 605-606. 1986) formally proposed A. laciniatum for rejection, but their proposal was rejected by the Nomenclature Committee for Pteridophyta (Pichi Sermolli, Taxon 36: 740-741. 1987).

Asplenium varians is variable, very similar to, and often confused with its ancestors, A. semivarians and A. tenuicaule (see above). Its relationships were discovered using hybridization experiments, chromosome counts, and micromorphology (Sleep & Reichstein, loc. cit.; Viane & Reichstein, Pterid. New Millennium, 73-105. 2003), showing it is an allotetraploid species that arose by chromosome doubling in the diploid hybrid between A. tenuicaule (A. tenuicaule var. subvarians in A. varians var. varians, and A. tenuicaule var. tenuicaule in the African A. varians var. fimbriatum) and A. semivarians. Two varieties are distinguished: A. varians var. varians, occurring in the Himalaya from N India into China (not in Japan), and var. fimbriatum, which is mainly found in S Africa (though its occurrence in S India needs further study). Asplenium paucijugum Ching is similar to A. semivarians but has larger spores and stomata. Further study is needed to show if this and related forms are autotetraploids of A. semivarians.

In places where Asplenium tenuicaule and A. varians grow together, their sterile hybrid is not uncommon.

In an outdated understanding of this complex, Fraser-Jenkins et al. (Indian Fern J. 27(1-2): 188. 2011) confusingly combined ancestral diploid and derived allotetraploid species and hybrids under a single amalgamate called Asplenium laciniatum, apparently ignoring hybridization experiments and cytological studies.