Trigonospora Holttum.

Plants medium-sized. Rhizomes creeping, decumbent or erect, bases with sparse lanceolate brown scales. Fronds remote, approximate or clustered; stipes usually with sparse short hairs, stramineous; laminae pinnate-pinnatifid, proximal pinnae gradually shortened into auricle, hastate or abruptly contracted into tubercule, pinnae attached to rachises and at base abaxially each usually with a dark brown tuberculate aerophore. Veinlets free, costules raised on both sides, proximal pair on adjacent segments sometimes reaching cartilaginous sinuses, rarely connivent, but usually acroscopic veinlet reaching sinus and basiscopic one reaching margin above sinus. Laminae usually deep green when dry, usually papery, sometimes herbaceous or leathery, laminae adaxially with dense appressed setae along costal grooves, sparsely setaceous also along veins, abaxially mostly with acicular hairs on intercostal areas, rarely glabrous. Sori orbicular, usually attached at middle of veinlets, sometimes at distal or proximal parts; indusia orbicular-reniform, thick, usually brown, persistent, with fine hairs or glabrous, sometimes glandular. Spores normally monolete, rarely trilete, exospore echinate, perispore cristate. x = 35, 36.

Pseudocyclosorus tibeticus Ching & Y. X. Lin (Acta Phytotax. Sin. 22: 201. 1984) was described from Xizang (Mêdog) but is excluded from the present treatment, pending further studies. It is similar to P. tylodes.

About 50 species: tropical and subtropical regions; 38 species (31 endemic) in China.

(Authors: Lin Youxing (林尤兴); Kunio Iwatsuki)