1Abaxial surface of rachis bearing slender terete spine-like scales.
1'Abaxial surface of rachis in most species lacking scales; scales, if present in this position, distinctly flat.
2Pinnae crenate to a depth of 1 mm
2'Pinnae much more deeply lobed.
3Pinnae 8-12 pairs, 6 cm or more apart
3'Pinnae to 20 or more pairs, closer together.
4Sori all elongate; veins not prominent on lower surface
4'At most basal sori elongate; veins rather thick and prominent beneath.
5Pinnae not over 3 cm wide, lobed ¼-2/5; basal sori only divergent but not elongate
5'Pinnae to 3.5 cm or more wide, lobed 2/5-3/5; basal 2-3 pairs of sori divergent and lowest elongate
6Basal veins not meeting but passing to sides of the sinus-membrane which is decurrent below their junction with it
6'Basal veins anastomosing or at least meeting below base of sinus-membrane which is not decurrent.
7Stipe scaly throughout; at least lower part of rachis scaly on abaxial side.
7'Stipe scaly near base only; rachis not scaly on abaxial surface.
8Pinnae to 3 cm wide, thin, drying light greenish; small indusia present.
8'Pinae not over 2.5 cm wide, firm, drying brown-olivaceous; no indusia.
9Capitate hairs abundant on lower surface of costae and costules; capitate hairs and sessile glands between veins
9'Glands mainly sessile, lacking between veins
10Rachis bearing slender terete scales on adaxial surface
10'Rachis lacking scales on adaxial surface, or such scales flat.
11Pinnae crenate to a depth of 1.5-3 mm; no indusia.
11'Pinnae lobed ⅓ towards costa or more deeply; indusia present in most cases.
12Lower surfaces covered with slender erect acicular hairs
12'Lower surfaces glabrous.
13Pinnae thin; veins not prominent beneath; sori close to costules except lowest
13'Pinnae firm; veins prominent beneath; several pairs of lower sori gradually divergent
14Lower surface bearing sessile glands
14'Lower surface bearing acicular and/or capitate hairs.
15Lower surface densely acicular-hairy throughout, lacking capitate hairs; no capitate hairs on sporangia
15'Lower surface bearing short capitate hairs at least on costules and veins; capitate hairs (rarely setae) present on sporangia.
16Pinnae thick and rigid; veins prominent on lower surface, grooved on upper surface
16'Pinnae thin; veins not prominent on lower surface nor grooved on upper surface.
17Basal pair of veins anastomosing to form a slender excurrent vein which is joined by the second acroscopic vein before entering base of sinus-membrane.
17'Basal pair of veins meeting, or not quite meeting, at base of sinus-membrane.
18Pinnae lobed less than half-way to costa; sori indusiate
18'Pinnae lobed more than half-way to costa; sori exindusiate