西南铁角蕨 xi nan tie jiao jue

Trichomanes aethiopicum N. L. Burman, Fl. Indica, 28. 1768; Asplenium adiantoides Lamarck; A. denticulatum Blume; A. furcatum Thunberg; A. praemorsum Swartz; Tarachia furcata (Thunberg) C. Presl.

Plants 25-45 cm tall. Rhizome short, erect to shortly creeping, scaly; scales dark reddish brown to black, narrowly triangular with a long filiform apical tail. Fronds caespitose; stipe 5-15(-22) cm, adaxially grayish green and sulcate, abaxially dark brown to black, with many reddish to dark brown, narrowly triangular scales with a long filiform apex; lamina narrowly ovate to narrowly triangular, 10-28 × 4.5-8 cm, apex acuminate, pinnate-pinnatifid to 2-pinnate; pinnae 10-15 pairs, subopposite or alternate, lower 1 or 2 pairs slightly reduced, subsessile, trullate-rhomboid with 1 or 2 (almost) free pinnules at base, 2.5-4.5 × 1-2.5 cm, base asymmetrical, broadly cuneate, apex acuminate; pinnules 2-4 pairs, obtrullate-elliptic or subflabellate, 4-12 × 2-5 mm, margin dentate, lateral sides entire, apex obtuse. Venation subflabellate, obvious abaxially, veins slender and forked, not reaching margin, costa grooved adaxially. Fronds leathery, adaxially dark green when dry and often grooved, abaxially brownish green, with reddish brown, fibrillose scales, subglabrous when old; rachis green but often becoming dark toward base abaxially, adaxially sulcate and densely scaly with fibrillose scales. Sori 2-5 per segment, linear, 3-8 mm, median on subtending veins; indusia grayish yellow, linear, membranous, entire, opening toward major veins or to costa, persistent. Plants polyploid, sexual or agamosporous.

On rocks in mixed forests; 1000-2600 m. Hunan, Jiangxi, Sichuan, Yunnan [India, Indonesia, Malaysia, Myanmar, Philippines, Thailand, Vietnam; tropical Africa, tropical America, Australia, Macaronesia, Pacific islands (Hawaii)].

Asplenium aethiopicum is a morphologically, ecologically, and karyologically very variable aggregate for which we prefer to use the oldest available epithet. Braithwaite (Cytotax. Invest. Asplenium aethiopicum Complex Africa, Ph.D. Thesis, University of Leeds. 1964; Bot. J. Linn. Soc. 93: 348-378. 1986), Panigrahi (Phytologia 31: 251-258. 1975), Manton et al. (Bull. Brit. Mus. (Nat. Hist.), Bot. 15: 123-161. 1986), and Ormonde (Bol. Mus. Munic. Funchal 43: 177-189. 1991; Acta Bot. Malac. 16: 293-315. 1991) have shown that A. aethiopicum s.l. is an aggregate of at least three sexual (A. aethiopicum subsp. tripinnatum (Baker) A. F. Braithwaite (4x), A. aethiopicum subsp. aethiopicum (8x), and A. aethiopicum subsp. dodecaploideum A. F. Braithwaite (12x)) and up to five apomictic taxa. Most of these cytotypes are common in Africa, but sexual tetraploids and dodecaploids are also known from Asia and America, where Swartz’s name, A. praemorsum, is used for the aggregate. Besides differing in chromosome number and pairing behavior, the members of this aggregate can also be separated on the basis of their exospore size. The agamosporous taxa can be distinguished from the sexual by the length/width ratio of their spores: agamosporous taxa have subglobose spores with a ratio smaller than 1.4, sexual taxa have reniform to plano-convex spores with a ratio larger than 1.4. Based on Braithwaite’s (Bot. J. Linn. Soc. 93: 343-378. 1986) key, Chinese specimens are probably sexual A. aethiopicum subsp. dodecaploideum but need cytological confirmation. We found hybrids with A. austrochinense in Jiangxi.