KEY TO THE SPECIES

1Fronds pinnatifid to pinnate
1'Fronds simple
2Fertile parts strongly contracted
2'Fertile parts similar to sterile part or slightly narrowed
3Fronds dimorphic, simple to pinnatifid, sori deeply sunken, hydathodes absent or infrequent
3'Fronds internally dimorphic, pinnate, sori superficial, hydathodes frequent.
4Hydathodes with persistent calcareous scales
4'Hydathodes without persistent calcareous scales
5Fronds pinnate
5'Fronds pinnatifid
6Lowermost pinnae not transversely inserted, vascular strands in the rhizome without sclerified bundle sheath, rhizome scales various but not shining
6'Lowermost pinnae transversely inserted, vascular strands in the rhizome with strongly developed sclerenchyma sheath, rhizome scales shining brown.
7Rhizome scales entire or weakly dentate, basal pinnae not cut out to costa at basiscopic base, veins on upper surface not raised
7'Rhizome scales strongly dentate at least at base, basal pinnae cut out to costa at basiscopic base, veins on upper surface raised
8Rhizome scales 9-17 mm long, thick, brittle, brown to blackish, entire, lower surface of lamina usually very distinctly glaucous (Philippines)
8'Rhizome scales smaller, thin, not brittle, lower surface of lamina not or slightly glaucous
9Sclerenchyma strands in the rhizome mainly peripheral, rhizome scales strongly dentate, veins on upper surface raised, sori slightly or deeply sunken.
9'Sclerenchyma strands in the rhizome scattered or mainly central, rhizome scales entire to short-dentate, veins on upper surface not raised, sori superficial.
10Fertile parts much narrower than sterile parts
10'Fertile parts similar to sterile part or somewhat narrower, or all fronds equally narrow, gramineous
11Coenosori present
11'Sori round, elongate or confluent, not forming continuous coenosori
12Coenosori transverse (sori confluent across connecting veins).
12'Coenosori longitudinal (sori confluent across veins)
13Rhizome scales acute, sori superficial
13'Rhizome scales contracted to a narrow acumen, sori deeply sunken.
14Rhizome scales pseudopeltate, margin of sterile fronds without notches.
14'Rhizome scales peltate, margin of sterile fronds with notches sporadically to regularly present
15Vascular strands in the rhizome without fully sclerified bundle sheath
15'Vascular strands in the rhizome with fully sclerified bundle sheath, sometimes 2 cells thick
16Sclerenchyma strands in the rhizome mainly central, hydathodes present, sometimes infrequent
16'Sclerenchyma strands in rhizome scattered, hydathodes absent
17Rhizome radial (at least in parts), sterile fronds narrow, 0.1-0.3 cm wide, index 6-18, sclerenchyma strands absent to many
17'Rhizome completely dorsiventral, sterile fronds mostly over 0.3 cm wide, index 2-7, sclerenchyma strands very many
18Rhizome not sclerified, rhizome scales narrow, 1-1.5 mm wide, remotely and weakly to strongly dentate
18'Rhizome with subperipheral sclerified sheath, rhizome scales wide, 1.8-3 mm wide, with a flabelloid, irregular margin
19Sori deeply sunken
19'Sori superficial or slightly sunken
20Rhizome scales elongated, 4.8-9 long, acute to acuminate, evenly brown; vascular strands in the rhizome 4; costa only distinct
20'Rhizome scales short, 3.8-4 mm long, obtuse to acute, with a distinct light margin; vascular strands in the rhizome 11-14; at least the veins distinct (simple forms)
21Vascular strands in the rhizome with fully sclerified bundle sheath, sometimes 2 cells thick
21'Vascular strands in the rhizome without fully sclerified bundle sheath
22Sori in 2-4 rows between costa and margin (form from Sulawesi).
22'Sori in one row between costa and margin
23Rhizome scales wide, 1.8-3 mm wide, margin entire, irregularly flabelloid, the ground tissue of rhizome with subperipheral sclerified sheath
23'Rhizome scales narrower, to 1.5 mm wide, margin dentate, ground tissue of rhizome not sclerified
24Fertile fronds shorter than sterile ones, sori large, spreading over the areole, covered with persistent scales, rhizome scales short-dentate
24'Fertile fronds usually longer than sterile ones, sori smaller, not spreading over the entire areole, without persistent scales, rhizome scales strongly dentate or long-ciliate
25Notches in fertile fronds absent, rhizome little elongated, internodes 0.5-2 cm long
25'Notches in fertile fronds regularly present, rhizome elongated, internodes 2.5-3 cm long
26Sclerenchyma strands in the rhizome few
26'Sclerenchyma strands in the rhizome many to very many
27Sori in two or more rows between costa and margin, in two rows between adjacent veins
27'Sori in one row between costa and margin, single between adjacent veins
28Fertile fronds narrow, to 0.3 cm
28'Fertile fronds wider, 0.6-1.6 cm
29Sori often longitudinally elongate or confluent into a coenosorus
29'Sori round, not elongate or confluent
30Rhizome scales strongly dentate, sclerenchyma strands in the rhizome scattered, sori large, elongate, all separate
30'Rhizome scales remotely and weakly dentate to short-dentate, sclerenchyma strands in the rhizome mainly central, sori small, separate, confluent or forming an interrupted coenosorus
31Lamina of fertile fronds 2-3 mm wide, sori often crossing the veins.
31'Lamina of fertile fronds 3-6 mm wide, sori separate or elongate, but not confluent across the veins
32Hydathodes absent, rhizome scales strongly dentate
32'Hydathodes frequent, rhizome scales remotely and weakly to short-dentate (form from Borneo: ‘kamborangana’)
33Hydathodes absent or infrequent
33'Hydathodes frequent
34Sori singly or in one row between adjacent veins (if indistinct follow this lead)
34'Sori distinctly in two or more rows between adjacent veins
35Rhizome scales obtuse, usually appressed
35'Rhizome scales acute or contracted to a narrow acumen
36Rhizome scales bicolorous, with a central or apical dark spot, not adhering to each other, sparsely set (most conspicuously on older parts of the rhizome), with distinctly cucullate apex (New Guinea)
36'Rhizome scales concolorous or nearly so, strongly overlapping and completely covering the rhizome, often with the margins strongly adhering to each other (forms from Sulawesi and the Moluccas)
37Sori deeply sunken
37'Sori superficial or slightly sunken
38Sori in two or more rows between costa and margin, veins distinct.
38'Sori in one row between costa and margin, costa only distinct
39Fertile parts narrowed, notches in fertile fronds regularly present.
39'Fertile parts similar to sterile part, notches absent or sporadically present.
40Fronds gramineous, less than 2 mm wide (gramineous form from New Guinea).
40'Fronds not gramineous, over 3 mm wide
41Vascular strands in the rhizome without fully sclerified bundle sheath
41'Vascular strands in the rhizome with fully sclerified bundle sheath, often 2 cells thick
42Rhizome scales contracted to a narrow subulate acumen, notches absent from lamina margin
42'Rhizome scales acute, notches sporadically or regularly present on lamina margin
43Sori in two or more more rows between costa and margin or in, usually interrupted, coenosori, veins distinct
43'Sori in one row between costa and margin, close to the margin, costa only distinct
44Medium-sized plants, lamina of fertile fronds 14-22 cm long, veins distinct, sori in 2-4 rows between costa and margin, rhizome scales very large, pseudopeltate
44'Small plants, lamina of fertile fronds 2.5 to 7 cm long, costa only distinct, sori in one row between costa and margin, rhizome scales small, peltate.
45Rhizome scales appressed (Luzon)
45'Rhizome scales spreading or squarrose
46Rhizome scales narrowly acuminate to subulate, squarrose
46'Rhizome scales obtuse to acute, not squarrose
47Fertile fronds narrow, to 1 cm wide, index 13-14, rhizome scales sparsely set and not fully covering the glaucous rhizome
47'Fertile fronds to 1.4 cm wide, index c. 10, rhizome scales dense, covering the rhizome
48Sori in two or more rows between costa and margin
48'Sori in one row between costa and margin
49Sori in one row between costa and margin
49'Sori in two or more rows between costa and margin
50Margin of fronds without notches, rhizome scales contracted to a subulate apex
50'Margin of fronds with notches sporadically to regularly present, rhizome scales acute, apex not subulate
51Sterile fronds 0.6-1 cm wide, fertile parts narrowed, rhizome scales evenly coloured
51'All fronds equally narrow, gramineous
52Rhizome short, internodes not elongated, scales pseudopeltate.
52'Rhizome slightly elongated, internodes to 0.5 cm, scales peltate
53Rhizome scales pseudopeltate, internodes not elongated (narrow forms).
53'Rhizome scales peltate, internodes distinctly elongated
54Margin cartilaginous, strongly thickened (New Guinea)
54'Margin not differentiated, or cartilaginous, but not strongly thickened
55Rhizome scales entire to short-dentate
55'Rhizome scales strongly dentate
56Lamina very gradually narrowed into the stipe, more or less spathulate, widest at or above the middle
56'Lamina distinct from the stipe, mostly lanceolate, widest at or below the mid-dle
57Rhizome scales peltate, costa with two distinct, narrow ridges on upper surface.
57'Rhizome scales pseudopeltate, costa flat or with low ridges on upper surface.
58Rhizome scales strongly dentate (Sumatra, some forms of S. enervis from New Guinea may also key out here)
58'Rhizome scales entire to short-dentate
59Rhizome scales not squarrose, acute
59'Rhizome scales squarrose, contracted to a narrow acumen.
60Margin of sterile fronds: notches frequent
60'Margin of sterile fronds: notches absent or infrequent
61Rhizome less than 1 mm thick, wiry
61'Rhizome over 2 mm thick, stout
62Fertile parts narrowed, sclerenchyma strands in the rhizome few.
62'Fertile parts similar to sterile part, sclerenchyma strands in the rhizome absent.
63Sori in two, sometimes more rows between adjacent veins
63'Sori in one row between adjacent veins
64Sori in 5 or more rows between costa and margin, with a slight but distinct rim around the receptacle, vascular strands in rhizome with fully sclerified bundle sheath, sclerenchyma strands absent
64'Sori in 1-4 rows between costa and margin, without rim around the receptacle, vascular strands in rhizome without fully sclerified bundle sheath, sclerenchyma strands many (some unusual forms from Sulawesi and New Guinea).
65Rhizome scales obtuse (an often trilobed form from Flores)
65'Rhizome scales acute or contracted to a narrow acumen
66Sori in 5 or more rows between costa and margin
66'Sori in one row between costa and margin (simple forms)
67Sori deeply sunken, hydathodes with conspicuous, persistent calcareous scales, rhizome scales contracted to a narrow, ciliate acumen, margin very strongly thickened, notches in fertile fronds regularly present
67'Sori superficial or slightly sunken, hydathodes without persistent calcareous scales, rhizome scales acute, entire or remotely and weakly dentate, fertile parts narrowed, margin not very strongly thickened, notches in fertile fronds absent or sporadically present (form from Seram)
68Sori in two, rarely more rows between adjacent veins
68'Sori in one row between adjacent veins
69Rhizome scales usually appressed, 2-3 mm wide, entire
69'Rhizome scales usually spreading, narrow, to 1 mm wide, dentate.
70Vascular strands in the rhizome without fully sclerified bundle sheath
70'Vascular strands in the rhizome with fully sclerified bundle sheath, sometimes 2 cells thick
71Rhizome scales remotely and weakly dentate, sori confluent or forming sometimes interrupted coenosori, hydathodes without persistent calcareous scales.
71'Rhizome scales strongly dentate or long-ciliate, sori round, hydathodes with persistent calcareous scales (simple forms)
72Coenosori usually long, sometimes interrupted (typical form)
72'Sori separate, (occasionally) confluent or in short coenosori, often a single row of sori along the costa slightly separate from the others (form from Philippines and Ternate)