Rhizome short to c. 15 cm long or occasionally up to 50 cm long, erect, suberect, or decumbent. Stipes reddish brown, of sterile fronds 6-35(-72) cm long, of fertile fronds 16-50(-88) cm long, base strongly or moderately enlarged, 5-15 mm wide in the middle, cross section one U-shaped vascular bundle, upper part of stipe tetragonal, aerophores present on stipe and rachis, slender, hook-shaped, with pointed apex. Fronds covered with an amorphous gelatinous mucilage layer when dry, dorsal side of rachis semiterete to trigonous or grooved, rachis (1-)2-4(-5) mm wide in the middle part. Sterile lamina rather thick, lower part pinnate, upper 1/3 to 1/2 pinnatifid, widest medially, 12-74 by (1.5-)3-13(-26) cm, index (2.5-)5-8(-11); pinnae (strongly ascending) (18-)30-60(-80) pairs, widest below or about the middle, veins of pinnae simple to as many as forked, distinct to obscure on both surfaces, margin entire, most pinnae except the uppermost with inequilateral to equilateral base, rounded to cuneate; lowermost pinnae sessile to shortly stalked, not deflexed, usually gradually shortened, some pinnae vestigial on stipe sided by aerophores (sometimes a few pairs); middle pinnae (1.3-)3.5-7(-18) cm long, (0.3-)0.5-1 cm wide in the middle, sessile to rarely shortly stalked, base rounded or cuneate (when dry); uppermost pinnae adnate, base unequal-sided, basiscopically decurrent into rachis wing to perpendicular to the rachis; apex of lamina pinnatifid, sometimes terminated by a pinnatilobed or a pinna-like segment. Fertile fronds usually longer than the sterile ones, sometimes shorter (or about the same length, sometimes from the high grasslands), dorsal side of rachis semiterete, trigonous or grooved, rachis (1-)2-4(-5) mm wide in the middle part; lamina pinnate except the apex, lower pinnae shortly stalked, 18-54(-90) by 3-12(-25) cm; pinnae sparsely short glandular hairy, 25-70 pairs, margin erose; lowermost pinnae gradually shortened, (0.8-)1-3(-6) cm apart; middle pinnae 3-14 cm long, 3-5 mm wide, base sessile, slightly cordate or shortly stalked; apex pinnatifid, acuminate or caudate. Paraphyses many, yellow to (glossy) brown. Spores brown, with reddish tubercles.
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