1Rhizome completely sclerified, scales basifixed, spores smooth
1'Rhizome with parenchymatous ground tissue, scales pseudopeltate or peltate, spores variously ornamented
2Fronds distinctly stalked, sori spread all over the lamina
2'Fronds sessile or indistinctly stalked, sori in an apical patch
3Phyllopods 1-2 cm apart. — Borneo
3'Phyllopods contiguous
4Hairs with all rays appressed or approximately equally spreading
4'Hairs with appressed rays and one elongated, erect spine. — Philippines.
5Sporangia in a longitudinal coenosorus
5'Sporangia in round or elongate, separate sori (fertile fronds absent follow this lead)
6Rhizome scales ciliate
6'Rhizome scales entire
7Rhizome scales elongate, over 5 times as long as wide, coenosorus sunken, paraphyses many, in a medial row in the coenosorus
7'Rhizome scales short, less than 3 times as long as wide, coenosorus superficial, paraphyses inconspicuous
8Stellate hairs dimorphic, sterile fronds mostly not wider than the basal part of the fertile ones
8'Stellate hairs monomorphic, appressed, sterile fronds much wider than the fertile ones
9Sori clearly in a single row between costa and margin
9'Sori in at least two rows between costa and margin (in doubt or fertile fronds absent follow this lead)
10Small plants, fertile fronds to 0.5 cm wide, indument monomorphic, appressed.
10'Medium to large plants, fertile fronds 1 cm wide or more, indument dimorphic, loose
11Scales brown (an aberrant form from Flores; compare also narrow forms of 19. P. rasamalae or 13. P. nummularifolia)
11'Scales with hyaline acumen
12Sori sunken
12'Sori superficial (or fertile fronds absent)
13Paraphyses mixed with the sporangia
13'Paraphyses in a central group in the sorus
14Rhizome flexible, scales ciliate
14'Rhizome rigid, scales entire
15Hydathodes absent
15'Hydathodes present
16Stellate hairs dimorphic, not appressed
16'Stellate hairs monomorphic, appressed
17Stellate hairs appressed, with boat-shaped straight rays
17'Stellate hairs with acicular straight rays, not appressed
18Rhizome scales dentate or ciliate
18'Rhizome scales entire
19Rhizome scales ciliate
19'Rhizome scales dentate
20Sterile fronds elongate, index 3-8, apex acute, fertile fronds not much narrowed.
20'Sterile fronds ovate to rounded, index 1-2, apex rounded, fertile fronds conspicuously narrowed
21Rhizome scales not squarrose, widest above the attachment, lamina to 62 (97) by 5.5 cm
21'Rhizome scales with long, sheathing base and squarrose acumen, widest near the attachment, lamina to 35 by 3 cm
22Scales with hyaline acumen, often squarrosely recurved(these two species are difficult to distinguish when sterile
22'Scales brown, spreading but not recurved
23Lamina 1.5-4 cm wide, rhizome scales 1.5-2.5 mm wide, usually widest above the attachment, sori to 2.5 mm, with many conspicuous paraphyses.
23'Lamina up to 1 cm wide, rhizome scales 0.4-1.4 mm wide, widest near the attachment, sori 1-1.5 mm, without conspicuous paraphyses.
24Lateral buds close to the phyllopods on the other side of the rhizome.
24'Lateral buds halfway between the phyllopods
25Rhizome without central sclerenchyma
25'Rhizome with a central sclerenchyma sheath (these two species are difficult to distinguish when sterile). 10. P. lanceolata or
26Sori deeply sunken, rhizome elongated with lateral buds close to but opposite the phyllopods
26'Sori superficial, rhizome short or elongated with lateral buds not close to the phyllopods
27Fronds distinctly long-stalked, the sterile fronds mostly ovate to elliptical, index 1-4
27'Fronds not stalked, or indistinctly stalked below a very gradually decurrent lamina, sterile fronds oblanceolate, index 6-20, or absent
28Rhizome scales dentate, stellate hairs sparse, thin, fugacious
28'Rhizome scales ciliate, stellate hairs forming a dense, persistent mat
29Rhizome scales with appressed, straight, ciliate apex
29'Rhizome scales with spreading, entire, crisped apex
30Rhizome short, phyllopods contiguous, rhizome scales pseudopeltate, stellate hairs monomorphic
30'Rhizome shortly elongated, phyllopods to 0.5 cm apart, rhizome scales peltate, stellate hairs dimorphic