PTERIDE2E PTERIS. 99 



on the lower side; sorus on a submarginal strand connecting the ends of the 

 veins, wanting in the sinus between the segments, protected by the reflexed 

 and specialized margin, without an extrorse indusium. A genus of 

 terrestrial ferns, most remarkable for the poor definition of the species. 

 Among our species, P. cretica and P. quadriaurita are especially notable for 

 the number :>f their more or less distinct forms and related species. 



1. Veins free. 



2. Fronds simply pinnate. 



3. Pinnae cuneate at base (1) p. opaca 



3. Pinnae truncate or cordate (2) P. longifolia 



2. Lowest pinnae forked or pinnate. 



3. Pinnules or segments of lowest pinnae 1 to 3. 

 4. F.ronds all equally pinnate. 

 5. Sterile fronds serrate. 



6. Stipes pale (3) P. cretica 



6. Stipes dark (4) P. melanocaulon 



5. Sterile fronds not serrate (5) P. pellucida 



4. Sterile fronds more pinnate than the 



fertile (6) P. ensiformis 



3. Segments or pinnules of lowest pinnae at 

 least 5. 



4. Only lower side pinnatifld (7) P. semipinnata 



4. Both sides incised. 



5. Only pinnatifld. 



6. Apex serrate (8) P. distans 



6. Apex entire (9) P. heteromorpha 



5. Pinnate P. dispar 



2. Lower pinnae at least bipinnatifid. 



3. Lowest pinnae not greatly enlarged. 

 4. Frond not over 1 m. high. 



5. Fronds all alike (10) P. quadriaurita 



5. Fronds dimorphous (11) P. grevilleana 



4. Frond well over 1 m. high (12) P. excelsa 



3. Lowest pinnae greatly enlarged (13) P. longipes 



1. Veins forming areolae along costa, otherwise free. 



2. Ultimate segments abruptly widened at base (14) P. patens 



2. Ultimate segments not abruptly widened. 

 3. Lowest pinnae of moderate size. 



4. Margin entire (15) P. biaurita 



4. Sterile margin crenate, large fern (16) P. Tcleiniana 



3. Lowest pinnae greatly enlarged (17) P. wallichiana 



1. Veins more copiously anastomosing (18) P. tripartita 



(1) P. opaca J. Sm. Stipe strong, erect, pale, finely pubescent; frond 

 60 to 90 cm. high, oblong, simply pinnate ; pinnae in numerous opposite pairs, 

 the largest 30 cm. long, narrowly linear, entire, cuneate at base, coriaceous, 

 glabrous except for the costa beneath ;. rachis pubescent like the stipe; veins 

 sunk in the frond and only visible as faint striations; indusium narrow, 

 brownish. 



Samar or Cebu, Cuming 342. 

 Celebes. 



(2) P. longifolia L. Stipes clustered, 15 to 30 cm. high, firm, erect, 

 pale, more or less clothed at the base with pale brown scales; frond 30 to 

 50 cm. high, 10 to 20 cm. broad, attenuate below, simply pinnate; pinna? 

 sessile, numerous, 10 to 15 cm. long, the lowest reduced, the upper linear, 



