46 A FLORA OF MANILA 



a longitudinal, incomplete annulus, interrupted by the stalk, opening trans- 

 versely. Indusium present or absent. 



Genera about 120, species nearly 5,000, in all parts of the world, 81 

 genera and about 700 species in the Philippines. 



1. Sori densely covering the entire back of the frond, or parts of the frond. 

 2. Fronds pinnate; very coarse terrestrial ferns of brackish swamps, the 



spofangia not gathered into sori 16. Acroatichum 



2. Fronds simple, entire; epiphytic ferns from creeping rootstock the 



sporangia in contiguous sori 14. Cyclophorus 



2. Fronds finely 3- or 4-pinnately divided, the ultimate segments small, 

 the fertile ones golden-yellow on the lower surface, the indusium 



consisting of the refiexed margins of the segments 10. Onychium 



1. Sori definite, on the back of the frond, scattered, or in regular rows, 

 not strictly marginal. 

 2. Fronds entire, dimorphous, the sori reticulate, following the nerves' 



over th? entire lower surface. 6. HemionitU 



2. Fronds pinnately lobed, pinnate, or decompound. 

 3. Sori round or nearly so. 

 -4. Indusium present. 



5. Pinnae articulated to the rachis 2. Nephrolepia 



5. Pinnae not articulated to the rachis.: ;... 1. Dryopteria 



4. Indusium. none. 



5. Fronds all alike 13. Polypodium 



5. Fronds dimorphous; basal, sterile, concave, humus-gathering ones 

 which are at first gr-'en, soon becoming brown, and ordinary 



green, pinnately lobed fertile fronds 15. Drynaria 



3. Sori elongated. 



4. Indusium wanting; finely pinnately compound ferns, the lower 



surface covered with white waxy powder 7. Ceropteriis 



4. Indusium present. 

 5. Veins forming regular areolae, or if not then the sori often 



double, on both sides of the veinlets 4. Athyrivm 



5. Veins not forming regular areolae, except sometimes at the 



margin, the sori always simple 5. Asplenium 



. Sori marginal, definite. 

 2. Indusium half cup-shaped, attached by the base and margins, opening 



outward _ 3. Da/oallia 



2. Indusium formed of the refiexed modified or unmojlified margin of the 

 frond. 

 3. Sori borne on J;he inner face of the reflexed' leaf-margin. 



, ~T> ... . ,.,.'-.. ■ ll- Admntum 



3. Sori not on the inner surf ace of the reflexed-margin, protected by 



it, but borne on the frond itself. 



4. Sori linear, on a strand connecting the tips of the veins, the 



reflexed margin of the leaf continuous; usually coarse, not 



finely divided ferns 12. Pteria 



4. Sori terminal on the veins, at first distinct, later confluent, the 

 reflexed margin of the leaf interrupted; slender, finely divided 



ferns _ 9. Cheilanthea 



2. Indusium none; otherwise very similar to Cheilanthea.... 8. NothoJaena 



