Plants medium-sized to large, terrestrial. Rhizomes short-creeping, decumbent or erect, slender to thick. Fronds close. Stipes grooved; cross section reveals a single U-, V-, or omega shaped vascular bundle. Blades 1-pinnate to 1-pinnate-pinnatisect; rachises grooved, straw colored to almost black, shiny, often winged, especially toward tips. Pinnae often pectinate, sometimes those toward base unequally forked or with large projections from winged costae; mostly glabrous; margins entire, dentate, or serrate. Veins free, 1- to 2-forked before forming partial or complete marginal commissural veins. Sori in long lines (coenosori) or short and divided (Pteris lidgatei), along margins on marginal commissural veins. False indusia formed by reflexed leaf margins.

A genus of about 250 species in tropical and warmer-temperate areas worldwide. Represented in Hawai 'i by three endemic, two indigenous, and one naturalized species.

KEY TO THE NATIVE AND NATURALIZED PTERIS SPECIES IN HAWAI'I

l. Blades 1-pinnate, becoming wider near tips; pinnae 8-21 pairs; stipes 1/10 frond length or less; blade tips similar to lateral pinnae but much longer; 225 all major islands .......................................... 6. P. vittata

l. Blades more divided than !-pinnate (occasionally 1-pinnate in P. lidgatei), not becoming wider at tips, usually less than 9 pinna pairs (up to 13 in P. excelsa); stipes more than 1/3 frond length; frond tips pinnatifid or terminal pinnae similar to but not longer than lateral pinnae (2).

2(1). Fronds 100-250 cm long; blades 1-pinnate-pinnatisect; rachises unwinged; pinnae pectinate with numerous, adnate segments cut to costae; ultimate segments narrow, lanceolate, on both sides of costae, cut nearly to costae; all major islands ......................................... 2. P. excelsa

2. Fronds 17-100 cm long (rarely to 150 cm in P. irregularis); blades 1-pinnatepinnatifid to 2-pinnate-pinnatifid, or 1-pinnate distally; rachises winged near tips, or nearly down to first pinna pair; basal 2-3 (or more) pinnae forked into subequal branches, or with large ultimate segments; ultimate segments few to several, large, sometimes pectinate projections mostly arising from lower pinna margins, cut to winged costae (3).

3(2). Sori variable, short, served by I or 2 veins, or coenosori served by more veins, or a mixture of both; blades thick and brittle; O'ahu (Ko'olau Mountains), Moloka 'i, West Maui ..................................... 5. P.lidgatei

3. Sori consisting of continuous coenosori served by many veins, extending along nearly full lengths of ultimate segment margins; blades chartaceous, not brittle (4).

4(3). Blades with only basal pinnae forked into 2 subequal branches, blades 1-pinnate distal to basal pinna pairs; rachises mostly unwinged or winged only at extreme tips; all major islands ......................... 1. P. cretica

4. Blades with several pinnatifid pinnae with lobes or with projections; rachiseswinged partially to almost entirely to basal pinnae (5).

5(4). Rachises winged only in 1/3-2/3 of blades; blades resembling those of P. cretica, but 1-3 basal pinna pairs unequally branched or with few to several irregularly scattered lobes and irregular projections from margins of pinnae; blade tips similar to lateral pinnae; all major islands ............................................. 3. P. hillebrandii

5. Rachises winged nearly to basal pinnae; all pinnae regularly lobed, not forked into unequal branches; blade tips pinnatifid; all major islands ............................................. .4. P. irregularis