Large clonal ferns with medium- to large-size fronds. Rhizomes deeply seated, very long-creeping, repeatedly branched (some branches more elongate and not producing leaves, others shorter and frondiferous), densely pubescent with pale to dark brown, multicellular hairs; stele complex, described as two, concentric, highly corrugated solenosteles. Leaves (fronds) produced singly and remotely at rhizome nodes, (30–)50–150(–250) cm long. Petioles (stipes) not sharply distinct basally from the rhizome, (10–)25–100 cm long, erect or ascending, shallowly to deeply grooved adaxially, glabrous, glabrescent or hairy, the trichomes usually a mixture of short white hairs and minute gland-tipped, reddish hairs (these mostly in the groove); vascular bundles several, forming a U-shaped, horseshoe-shaped, or Ω-shaped pattern in cross-section. Laminae (blades) 20–150(–200) × 15–100 cm, broadly deltate to deltate-triangular, ovate-triangular, or nearly pentagonal, 2-pinnate-pinnatifid to 3-pinnate-pinnatifid (proximally), the pinnae mostly opposite to subopposite; proximal pinnae often prolonged basiscopically, the rachis and costae shallowly to deeply grooved with confluent, grooves, lacking prickles, pubescent similar to the petiole; small glandular patches (nectaries) present at bases of proximal and sometimes also distal pinnae; pinnules short to elongate, unlobed or few- to many-lobed, the lobes triangular to narrowly oblong or oblong-linear, rounded to pointed at the tips, the margins strongly reflexed; tissue chartaceous to somewhat coriaceous, abaxially glabrous to more commonly variously hairy (sometimes only on the costae and veins), adaxially glabrous or very sparsely hairy, except sometimes near the margins; veins mostly 1-forked, the branches often confluent marginally into a commissural vein. Sori an uninterrupted submarginal band along the commissural vein; excurrent true indusium absent or vestigial, a very slight ridge; pseudoindusium strongly developed, consisting of the recurved pinnule margin, this often white or pale, erose and often sparsely to densely long-ciliate. Sporangia with well-developed, triseriate stalks, the vertical annulus usually with a well-developed stomium. Spores 64 per sporangium, trilete, tetrahedral-globose, 23–32 μm in diameter, brown; perispore irregularly granular; exospore thin, undulate. Source documents: Tryon (1941), Tryon and Tryon (1982), Kramer (1990), Tryon and Lugardon (1991), Jacobs and Peck (1993), Mickel and Smith (2004).
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