Rhizome short to c. 15 cm long, erect to decumbent, narrow and very woody. Stipes of sterile fronds (2-)12-30(-40) cm long, of fertile fronds (4-)24-45 cm long, base strongly enlarged, 3-15 mm wide in the middle, cross section one U-shaped vascular bundle, upper part of stipe tetragonal, aerophores present on stipe and rachis (sometimes absent on stipe, and not prominent), slender, hook-shaped, with pointed apex (usually). Fronds covered with an amorphous gelatinous mucilage layer when dry, dorsal side of rachis grooved (usually), flattened, semiterete, or trigonous, rachis (0.5-)2-3(-5) mm wide in the middle part. Sterile lamina rather thick, pinnate except the pinnatifid or pinnatilobed apex or lower part, upper 1/3 to 1/2 pinnatifid, widest medially to subbasally, (5-)30-60(-100) by (2.5-)13-22(-27) cm, index (1.68-)2-3.85(-6.13); pinnae (6-)17-39 pairs, widest below or about the middle, veins of pinnae simple to, rarely, as many as forked, distinct to obscure on both surfaces, margin entire or rarely serrulate, most pinnae except the uppermost with equilateral to inequilateral base, cuneate to rounded; lowermost pinnae shortly stalked (sometimes stalk up to 1 cm long), not deflexed, gradually to abruptly shortened (2 or 3 pairs); middle pinnae (1.5-)6-14 cm long, (0.4-)0.7-1.4(-1.9) cm wide in the middle, sessile to shortly stalked, base rounded or cuneate; uppermost pinnae adnate, base unequal-sided, basiscopically decurrent into rachis wing or rounded; apex of lamina pinnatifid or terminated by a pinna-like (2-7 cm long) or pinnatilobed, long-triangular segment, rarely terminated by a pinna conform to lateral ones with free base, shortly stalked, 11 cm long. Fertile fronds usually longer than sterile ones, dorsal side of rachis grooved, flattened, or semiterete, rachis 1-4(-5) mm wide in the middle part; lamina pinnate, pinnae stalked, uppermost pinnatifid, pinnae base decurrent, (12-)35-60(-100) by (2-)9-15(-30) cm; pinnae sparsely bearing short glandular hairs or glabrous, 16-30 pairs, margin erose; lowermost pinnae not shortened (short to long stalked, rarely one or two pairs shorter), (2-) 4(-8) cm apart; middle pinnae (2.5-)7-13(-22) cm long, (3-)4-5(-6) mm wide, base shortly stalked; apex pinnatifid, terminated by a pinna-like segment (usually 2-4 cm long). Paraphyses many, dark brown or yellow. Spores brown, with reddish tubercles.
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