1Stipe and rachis bearing ± copious dark spines (bases of former scales); sori in most cases exindusiate.
1'Stipe (except base) and rachis smooth; scales, if present, not spine-like; sori in almost all species indusiate.
2Pinnae not over 4.5 cm wide; costules not over 5 mm apart.
2'Largest pinnae 7-12 cm wide with costules 10-12 mm apart.
3Pinnae to 4.5 cm long; pinna-lobes concave beneath; stipe-scales to 4 mm long.
3'Pinnae larger; pinna-lobes not concave beneath; stipe-scales 8 mm or more long.
4Sori exindusiate.
4'Sori indusiate
5Sporangia bearing several long setae
5'Sporangia lacking setae.
6Pinnae to 9x 1.2 cm; basal veins both passing to margin above base of sinus
6'Pinnae of well-grown plants much larger; basal veins both ending beside sinus-membrane.
7Stipe-scales terete at base and apex, less than 0.5 mm wide in middle; pinnae to 4.5 cm wide
7'Stipe-scales flat except at base, largest at least 1mm wide; pinnae rarely more than 3 cm wide
8All pinna-lobes or pinnules auricled at base on basiscopic side; veins forked or pinnate in the auricles
8'Pinna-lobes not thus auricled.
9Pinnae lobed almost to costae; lobes not separately adnate
9'Pinna-lobes in basal half of pinnae separately adnate to costa
10Pinnae 1-5 pairs; apical lamina pinna-like; costules 5-7 mm apart
10'Pinnae commonly to at least 10 pairs, or if fewer costules 3-4 mm apart.
11No indusia; no setae on sporangia.
11'Indusia present, or if absent all sporangia setiferous.
12Aerophores elongate; sori near costules
12'Aerophores not elongate; sori medial
13Sporangia all setiferous; no glands present.
13'Sporangia usually with glands; setae, if present, short and not on all sporangia, sometimes alternating with glands.
14Sori supramedial; sporangia with 1-3 short setae
14'Sori medial or inframedial; sporangia bearing several long setae.
15Veins 10-12 pairs; largest pinnae not over 12 X 2.5 cm, almost sessile.
15'Veins 14-16 pairs; largest pinnae 21 x 3.3 cm, with stalks 3-4 mm long.
16Sori supramedial.
16'Sori medial or inframedial.
17Pinnae to 20 x 3 cm; veins 15-18 pairs.
17'Pinnae smaller; veins not over 12 pairs.
18Indusia overlapping margin; basal acroscopic lobe of lower pinnae elongate with forked veins
18'Indusia not overlapping margin; basal acroscopic lobe of lower pinnae not enlarged
19Both basal lobes on basal pinnae free and short-stalked
19'Basal lobes of basal pinnae not free
20Pinna-lobes on both sides of costa conspicuously falcate.
20'Pinna-lobes not conspicuously falcate on both sides of costa.
21Upper surface glabrous between veins; pinnae 8 pairs
21'Upper surface bearing hairs between veins; pinnae 20 pairs.
22Hairs on lower surface of rachis and costae 1 mm long, on upper surface between veins appressed
22'Hairs on lower surface of rachis and costae 0.3 mm long, on upper surface between veins short-erect
23Basal 10-12 pairs of pinna-lobes separately adnate to costa
23'At most 1 free pinna-lobe separately adnate.
24Pinnae to 25 x 5 cm, all except distal ones stalked; lower pinnae with stalks 3-6 mm; indusia small, caducous
24'Pinnae smaller; most pinnae almost sessile, basal ones with stalks at most 2-3 mm long; indusia firm, persistent.
25Veins 20 pairs or more.
25'Veins 10-15 pairs.
26Basiscopic lobes of all pinnae strongly falcate and shorter than acroscopic lobes; basal scales to 20 mm long, very narrow
26'Basiscopic lobes, if falcate, not or little shorter than acroscopic; basal scales much shorter, usually wider.
27Basal acroscopic lobe of basal pinnae free, wider than the rest, with some forked veins
27'Basal acroscopic lobe of basal pinnae otherwise.
28Lower surface quite glabrous.
28'Lower surface of costules at least bearing acicular hairs.
29Pinnae c. 11x2 cm; basal acroscopic lobe of basal pinnae reduced.
29'Pinnae c. 22 x 3 cm; basal acroscopic lobe of basal pinnae elongate.
30Pinnae lobed to 0.5 mm from costa
30'Pinnae lobed to 1-2 mm from costa.
31Basal pinnae with stalks 2 mm or more long.
31'Basal pinnae sessile or nearly so.
32Pinnae lobed to 1.5-2 mm from costa
32'Pinnae lobed to less than 1 mm from costa.
33Basal scales thick, narrow; sori a little inframedial
33'Basal scales c. 5 x 1.5 mm; sori near costules
34Pinnae to 6 cm long; lobes on basiscopic side strongly falcate, on acroscopic side almost straight
34'Pinnae longer; lobes on basiscopic side not greatly different from those on acroscopic side.
35Aerophores small, dark; sori medial or a little inframedial.
35'Aerophores pale, slender, 1 mm long; sori near costules
36Some sporangia bearing setae
36'Sporangia lacking setae, glands usually present