42. Asplenium indicum Sledge, Bull. Brit. Mus. (Nat. Hist.), Bot. 3: 264. 1965.
胎生铁角蕨 tai sheng tie jiao jue
Asplenium laciniatum D. Don var. planicaule C. Christensen; A. planicaule Wallich ex Mettenius (1859), not E. J. Lowe (1858); A. wuyishanicum Ching; A. yoshinagae Makino subsp. indicum (Sledge) Fraser-Jenkins; A. yoshinagae var. indicum (Sledge) Ching & S. K. Wu; A. yoshinagae var. planicaule (C. Christensen) C. V. Morton.
Plants 10-25 cm tall. Rhizome erect, short, scaly; scales dark to reddish brown, narrowly triangular, entire, apex acuminate. Fronds caespitose; stipe grayish brown or grayish green to stramineous, 5-10 cm, adaxially grooved longitudinally, with small scales similar to rhizome scales, subglabrous when old; lamina narrowly triangular, 7-25 × 2-5 cm, apex acuminate, 1-pinnate; pinnae 8-20 pairs, alternate or lower ones opposite, shortly stalked, basal pinnae not or slightly reduced, middle pinnae 1-2.5 × 0.5-1.3 cm, rhomboid to trapezoid or subdimidiate, ± falcate, base asymmetrical, first acroscopic lobe larger than first basiscopic lobe, acroscopic side truncate, almost parallel to rachis and auriculate, basiscopic side narrowly cuneate (1/4-1/3 cut off) to almost parallel to costa, margin irregularly bicrenate, apex acute to acuminate, rarely obtuse. Veins obvious, grooved adaxially, basal acroscopic vein multi-forked, other veins 1- or 2-forked. Fronds subleathery, grass-green to stramineous when dry, adaxially with wrinkles above veins, with small, brown, narrowly triangular and apically filiform scales on abaxial surface and pinna stalks, subglabrous when old; rachis (when dry) abaxially grayish castaneous to green-stramineous for most of its length, and with small narrowly triangular and apically filiform scales, adaxially longitudinally valleculate, often with scaly gemmae or juvenile plants on pinna stalks or rachis. Sori linear, 3-7 mm, from near costa running nearly to margin, distal sori close to rachis; indusia grayish brown, linear, entire, opening toward costa or first acroscopic vein. Spores with lophate (costate) perispore, average exospore length 31-36 µm. Plants tetraploid: 2n = 144.
On wet rocks or tree trunks in forests; 600-2700 m. Anhui, Fujian, Gansu, Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Bhutan, India, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam].
Asplenium indicum is a sexual tetraploid plant in India, the Himalaya (Mehra & Bir, Curr. Sci. 26: 151-152. 1957; Bir, Curr. Sci. 29: 445-447. 1960; Curr. Sci. 31: 248-250. 1962; Caryologia 18: 107-115. 1965), and China (Guizhou, Xizang). It is morphologically very variable and similar to A. yoshinagae with which it is often united to form an aggregate taxon. Because they are genetically isolated and form sterile hybrids when growing together, we treat these taxa as separate species. In China, A. indicum is usually a smaller plant, with smaller spores and stomata than A. yoshinagae, from which it can also be distinguished by a chromosome count or flow-cytometry. The distinction based on the presence of gemmae is highly unreliable, at least in China, where all tetraploids checked were gemmiferous. The gemmae are formed on the pinna stalks, close to the rachis, rarely on the rachis itself. Another very similar taxon, A. gueinzianum, is also gemmiferous but produces buds on the surface of the pinnae. Due to confusion among these taxa, the exact distribution of this species is not well documented.