Rhizome short to c. 15 cm long or occasionally up to 50 cm long, erect, suberect, or decumbent, narrow, sometimes very woody. Stipes reddish brown, of sterile fronds (0.5-)3-35(-72) cm long, of fertile fronds (2.5-)6-55(-88) cm long, base slightly, strongly, or moderately enlarged, 0.5-20 mm wide in the middle, cross section one U-shaped or one V-shaped vascular bundle, upper part of stipe tetragonal, terete, or oval, aerophores present on stipe and rachis, only on base of stipe, or seemingly absent when dry, slender, hook-shaped, with pointed apex (usually); stipes and rachises glabrous. Fronds usually in var. latipinna covered with an amorphous gelatinous mucilage layer when dry, dorsal side of rachis semiterete, trigonous, flattened or grooved, not winged, rachis (0.2-)0.5-4(-5) mm wide in the middle part. Sterile lamina subcoriaceous, not glaucous, rather thick to rather thin but firm, pinnate except the pinnatifid or pinnatilobed apex or lower part pinnate, upper 1/3 to 1/2 pinnatifid, except a few free basal pinnae, or rarely pinnatifid throughout, widest medially to subbasally, (4-)12-74(-100) by (1-)2.5-22(-27) cm, index (1.68-)2-8(-11); pinnae (6-)17-60(-80) pairs, widest near base to about the middle, veins of pinnae simple, paired at base, forked above base, or simple as many as forked, distinct, obscure, or invisible on both surfaces, stomata scattered on the lower epidermis, margin (sometimes except the apex) entire, crenate or serrulate, most pinnae except the uppermost with equilateral or inequilateral base, acroscopic side adnate, cuneate, rounded, auriculate or attenuate; lowermost pinnae sessile, shortly stalked or rarely adnate but slightly constricted, deflexed or not, slightly, gradually, or abruptly shortened, not reduced or rarely some pinnae vestigial on stipe sided by aerophores; middle pinnae (0.5-)1-14(-20) cm long, (0.15-) 0.4-1.4(-1.9) cm wide in the middle, sessile to shortly stalked, base rounded, cuneate, or auriculate; apex of lamina pinnatifid, terminated by a pinnatilobed segment or rarely by a pinna conform to lateral ones. Fertile fronds usually longer than the sterile ones, rarely shorter or about the same length, dorsal side of rachis semiterete, flattened or grooved, not winged, rachis 0.5-4(-5) mm wide in the middle part; lamina pinnate throughout, pinnae nearly sessile or shortly stalked, or pinnate except the apex and lower pinnae shortly stalked, or pinnate with stalked pinnae, uppermost pinnatifid, pinnae base decurrent, (6-)11-60(-100) by (0.7-)1.5-20(-30) cm; pinnae sparsely bearing short glandular hairs or glabrous, 15-72 pairs, margin erose, entire, or subentire; lowermost pinnae the longest or gradually shortened, 0.5-4(-8) cm apart; middle pinnae (0.4-)0.8-14(-22) cm long, 1.5-6 mm wide, base slightly cordate, shortly stalked, or sessile (rarely auriculate or with one basiscopic lobe); apex pinnatifid, acuminate or caudate, rarely terminated by a pinna-like segment. Paraphyses many or few, mostly lost or absent, yellow, brown, or dark brown. Spores brown or yellow, with reddish tubercles.
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