1Veins free or with irregular slight anastomosis
1'Veins anastomosing in sterile fronds
2Pinnae c. 3 cm long; veins 3 or 4 pairs, nearly all simple
2'Pinnae much longer; veins 6 or more pairs, mostly forked
3Sori indusiate
3'Sori exindusiate
4Hairs between veins scattered all over upper surface
4'Hairs between veins on upper surface present only near sinuses and margins of pinna-lobes
5Pinna-lobes at most crenate
5'Pinna-lobes, except those of distal pinnae, distinctly lobulate.
6Lamina of largest fronds 30-40 cm long; suprabasal fertile pinnae to 12 × 2.5 cm
6'Lamina of largest fronds 50-75 cm long; suprabasal fertile pinnae to 15 cm or more long, 2.5-4 cm wide
7Stipes rusty brown, not glossy
7'Stipes nearly black, glossy
8Fertile pinnae not greatly contracted; most sori separate
8'Fertile pinnae with lobes much contracted
9Young fertile fronds with distinctly separate sori
9'Young fertile fronds with sporangia running along all veins and at maturity covering lower surface of pinna-lobes
10Young sori round, indusiate, on pinna-lobes 1.5-2.5 mm wide, completely cover ing lobes when mature
10'Young sori of varied form; if indusiate on much wider pinna-lobes which they do not cover when mature
11Sori all irregularly elongate along veins, exindusiate
11'Sori all round to elliptic, not linear, indusiate or not
12Suprabasal pinnae of mature plants to 13 × 2.5 cm, lacking costular aréoles; no buds on upper surface of sterile fronds.
12'Suprabasal fertile pinnae of mature plants to 25 × 5 cm; several pairs of costular aréoles present; buds present on upper surface of some costae of sterile fronds near the rachis
13Sori in one row on each side of costules of pinna-lobes
13'Sori on each side of veins which run to crenatures on margins of pinna-lobes
14Basal pinnae of fertile fronds bearing 1 pair of free pinnules and 2 or 3 pairs adnate
14'Basal pinnae of fertile fronds lacking pinnules
15Fronds to 70 cm long; sterile pinnae to 21 × 4 cm.
15'Fronds to 30 cm long; sterile pinnae much smaller