石生铁角蕨 shi sheng tie jiao jue

Asplenium affine Swartz var. sinense Christ; A. comptum Hance (1866), not Kunze ex T. Moore & Houlston (1852); A. dimidiatum Swartz var. comptum Baker.

Plants 20-50 cm tall. Rhizome erect, short, scaly; scales dark brown, narrowly triangular, margins dentate-fimbriate. Fronds caespitose; stipe grayish green to black, 10-22 cm, base scaly, more sparsely so upward, adaxially sulcate; lamina triangular-ovate to narrowly triangular, 12-28 × 5-11 cm, pinnate or pinnate-pinnatifid to 2-pinnate at base and gradually becoming pinnate toward apex, apex acute; terminal apical pinna simple or pinnatifid; pinnae 5-12(-14) pairs, simple or pinnate (basal pinnae), opposite or alternate, stalk 5-12 mm; basal pinnae usually largest, 3-6 × 2-3 cm, rhomboid or triangular to narrowly triangular, base asymmetrical, acroscopic side truncate to cuneate, basiscopic side cuneate, margin irregularly crenate-sinuate, apex acute to acuminate; segments 1-3, rhomboid to elliptic or obovate, 0.6-2 × 0.3-1.2 cm, basal acroscopic segment largest. Costa shallowly sulcate adaxially, lateral veins flabellately forking, not reaching margin. Fronds leathery, dark brown when dry; rachis dark brown to grayish black at base, becoming green toward apex, with dark brown, narrowly triangular scales with lateral fimbriae and filiform apex, subglabrous when old, adaxially sulcate. Sori 3-6 per segment (8-12 on basal acroscopic segment), linear, 4-15 mm; indusia brown, linear, thickly membranous, entire, opening toward costa or major veins. Spores with dark brown, lophate perispore, average exospore length 26-29 µm (in tetraploids) or 40-45 µm (in octoploids).

On limestone rocks in forests; 300-1300 m. Guangdong, Guangxi, Guizhou, S Hunan, Sichuan, Yunnan [Vietnam].

Asplenium saxicola is an aggregate of tetraploid and octoploid plants with fronds similar, though more divided at the base, to those of A. dimidiatum Swartz (America) and A. hemitomum Hieronymus and A. megalura Hieronymus (Africa). The scales are similar to those of A. aethiopicum but have thicker cell walls and a shorter apical tail. The ploidy level of plants from the type locality in Guizhou is not known. Tetraploids were found in Guangxi and octoploids in Guangxi and in Yunnan.