KEY TO THE SPECIES of Pronephrium Subg. Pronephrium Sect. Pronephrium

1Pinnae of fronds of adult plants about equal in size to apical lamina.
1'Apical lamina much larger than pinnae, or fronds simple.
2Glands present on lower surface of pinnae
2'Glands lacking on lower surface of pinnae.
3Pinnae 2-3 pairs; glands present on indusia or sporangia or both
3'Pinnae to at least 7 pairs; no glands on indusia and sporangia.
4Pinnae to 30 x 5 cm; spores with a median wing and cross-wings
4'Pinnae to 15 x 2.5 cm; spores with many separate small wings.
5Sori exindusiate; glands usually lacking on lower surface between veins.
5'Sori indusiate; glands always present on lower surface between veins.
6No free pinnae; sometimes one small pair broadly adnate
6'Free pinnae present on adult plants.
7Sporangia bearing glands near annulus.
7'Sporangia bearing setae, not glands, near annulus.
8Apical lamina to 20 x 3.5 cm; midrib of apical lamina and rachis glabrous on lower surface
8'Apical lamina to 6x1.7 cm; hairs present on lower surface of midrib of apical lamina and rachis
9Terminal lamina lobed ¼-⅓ towards midrib; pinnae to at least 1 cm long.
9'Terminal lamina crenate; pinnae 2-5 mm long
10Pinnae 4-8 cm long
10'Pinnae not over 2 cm long.
11No glands on lower surface
11'Glands present on lower surface
12Veins in basal part of apical lamina forked, their branches anastomosing.
12'Veins in apical lamina not forked
13Apical lamina widest near its base; pinnae 1 pair
13'Apical lamina not widest near its base; pinnae 3 pairs, decreasing downwards