2. Pteridium Gleditsch ex Scopoli, Fl. Carniol. 169. 1760.
蕨属 jue shu
Authors: Wenbo Liao, Ding Mingyan, Zhaohong Wu & Jefferson Prado
Filix Ludwig (1757), not Séguier (1754), nor Adanson (1763).
Plants terrestrial, robust. Rhizome brownish black, thick, ca. 5 mm in diam., hypogeal, densely clothed with rusty yellow to castaneous hairs, without scales. Fronds 50-130 cm; stipe with several vascular bundles; lamina large, often ovate or ovate-triangular, subleathery to papery, abaxially ± pilose, adaxially glabrous or sparsely hairy, 3- or 4-pinnate-pinnatifid; costae of ultimate pinnae clothed with fine gray-brown hairs, rarely glabrescent; rachises grooved adaxially, glabrous or pubescent; pinnae subopposite or alternate, stalked, basal pinnae pair larger than other pinnae, triangular; venation of ultimate pinnae pinnate, veins 2-forked, adaxially conspicuously prominent. Sori submarginal, linear, paraphyses not present; indusia formed by two layers; outer layer consisting of thin reflexed margin of lamina, persistent; inner layer thinner, vestigial, not conspicuous, sometimes nearly degenerate; sporangia long stalked; spores trilete, with low nipple-shaped protuberances. x = 13.
About 13 species: widely distributed worldwide, but mainly in the tropics; six species (three endemic) in China.
