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

1Sori exindusiate.
1'Sori indusiate.
2Pinnae not more than 3 cm long.
2'Pinnae longer on mature plants.
3Upper surface short-appressed-hairy; sori elongate
3'Upper surface glabrous; sori not elongate
4Fertile pinnae 2 mm wide
4'Fertile pinnae to at least 1 cm wide.
5Surfaces between veins glabrous.
5'Surfaces both short-hairy between veins.
6Sporangia setiferous
6'Sporangia not setiferous.
7Pinnae 2-3 cm wide
7'Pinnae not over 1 cm wide
8Pinnae c. 15 pairs
8'Pinnae 2-3 pairs
9Fronds simple, 10-20 cm long with cordate base
9'Fronds pinnate or, if simple, smaller and sterile.
10Lower surface between and/or on veins bearing sessile spherical glands.
10'Lower surface between and on veins lacking sessile spherical glands.
11Veins free
11'Veins anastomosing.
12Free pinnae not over 7 pairs, not over 2.0 cm wide.
12'Free pinnae more numerous or wider.
13Hairs on lower surface of costules and on upper surface between veins not appressed
13'Hairs on lower surface of costules and on upper surface appressed.
14Indusium bearing glands
14'Indusium bearing hairs
15Lower pinnae with stalks 1-2 mm long
15'Lower pinnae sessile.
16Hairs on lower surface of costae and costules erect
16'Hairs on lower surface of costae and costules slender, appressed.
17Sterile and fertile pinnae both 8-9 cm long
17'Sterile and fertile pinnae dimorphous, smaller.
18Sterile pinnae c. 4.5 x 1.4 cm; rachis almost glabrous on abaxial surface
18'Sterile pinnae c. 2.0 x0.8 cm; rachis bearing copious erect hairs on abaxial surface
19Glands present on sporangia, in some cases setae also.
19'Sporangia lacking glands; setae present in most cases.
20Fertile pinnae 3-4 mm wide; sterile to 10 mm wide
20'Fertile pinnae 10 mm or more wide; little dimorphism.
21Pinnae 6-10 pairs; sporangia bearing small glands only.
21'Pinnae 3-4 pairs; sporangia often with both glands and setae.
22Pinnae 2-3 cm wide
22'Pinnae not over 1 cm wide
23Fertile pinnae less than 1.5 cm long; sori in 1 row on each side of costa.
23'Fertile pinnae to at least 2 cm long; sori in several rows.
24Pinnae and/or frond-apex on both young and adult plants ± dilated and irregularly lobed distally
24'Pinnae not thus dilated nor irregularly lobed.
25Basal pinnae narrowly cuneate at base both sides, not auricled; fertile pinnae not or little narrower than sterile
25'Basal pinnae otherwise, usually auricled; fertile pinnae in most cases narrower than sterile.
26Indusia not very small, bearing many short hairs.
26'Indusia small, with dark red cell-walls; marginal hairs few or none.
27Upper surface of pinnae bearing short suberect hairs between veins.
27'Upper surface glabrous between veins.
28Pinnae 7 pairs; indusia thin with some superficial hairs.
28'Pinnae 15 pairs; indusia firm with stiff marginal hairs
29Sporangia setiferous.
29'Sporangia lacking setae.
30Sterile pinnae barely 1 cm wide
30'Sterile pinnae commonly 2 cm or more wide.
31Sterile pinnae entire, to 13 x 4 cm
31'Sterile pinnae crenate, to 11 x 2.5 cm
32Indusia firm, almost circular, with hairs in the middle
32'Indusia thin, shrivelled when dry, hairy throughout.
33Sterile pinnae crenate, at least distally
33'Sterile pinnae entire
34Fertile pinnae 1.5 cm or more wide
34'Fertile pinnae not more than 1 cm wide.
35Sterile pinnae not or little more than 1 cm wide, fertile 3-6 mm wide.
35'Sterile pinnae 1.5 cm or more wide, fertile 5-10 mm wide
36Pinnae thick; lower surface glabrous with thick pale prominent veins
36'Pinnae thin; hairs present on lower surface of costae; veins concolorous, not prominent.
37Pinnae to 15 pairs, sterile ones 4-6 cm long, narrowly acuminate.
37'Pinnae not over 10 pairs, sterile ones shorter, abruptly pointed.