POLYPODIACEAE. 



465 



A. Sori confluent, without indusia, covering the under side of 



leaf -segments ; large pinnate marsh ferns. 



B. Sori separated, or forming marginal rows on the under side 



of leaves or of leaf-segments. 



1. Sori marginal or submarginal. 



a. Sori without indusia. 



Leaves grass-like : venation regularly areolate, with- 

 out included veinlets 



Leaves narrow ; venation irregularly areolate, with 

 numerous included veinlets. 



b. Sori with indusia. 



Indusia formed of the inrolled margins of leaf- 

 segments. 



Sori forming a continuous marginal band. 

 Indusia double. 

 Indusia simple. 



Sori borne on leaf-lobes at the ends of veins. 

 Indusia cup-like at the truncate ends of leaf -segments. 



2. Sori dorsal. 



1. Sori linear or oblong, more than twice as long 



as wide. 



Sori parallel to the midvein of leaf-segments. 

 Sori oblique to the midvein. 



2. Sori orbicular or nearly so. 



a. Sori without indusia. 



Sori nearly confluent ; leaves much divided, 



powderv beneath. 



Sori distinctly separated ; leaves not powdery. 

 Veins free. 

 Veins anastomosing. 

 Leaves pinnatifld. 

 Leaves entire. 



Small-leaved, climbing ferns. 

 Large-leaved, tufted ferns. 



b. Sori with indusia (indusia vestigial or wanting 



in species of Dryopteris). 

 Sori borne on the backs of veins. 



Veins copiously anastomosing, the areoles ir- 

 regular. 

 Veins free or, if anastomosing, the areoles 



regular. 



Sori borne at the ends of veins ; indusia large, 

 reniform or orbicular. 



1. Acrostichum. 



2. Vittaria. 



3. Paltonium. 



A. Pteris. 



5. Pycnodoria. 



6. Adiantum. 



7. Sphenomeris. 



8. Blechnum. 



9. Asplenium. 



10. Pit yro gramma. 



11. Polypodium. 



12. PTilebodium. 



13. Phymatodes. 



14. Campyloneuron. 



15. Tectaria. 



16. Dryopteris. 



17. Nephrolepis. 



1. ACKOSTICHUM L. Sp. PI, 1067. 1753. 



Swamp-inhabiting, large ferns, with pinnate leaves growing in crowns. 

 Sporanges spread over the whole surface of the leaf -blades, or of the upper 

 segments.' Veins forming copious areolae without free veinlets. [Greek, signi- 

 fying a summit row.] A few species, natives of warm temperate and tropical 

 America. Type species: Acrostichum aureum L. 



Petiole usually armed with spurs ; venation of the pinnae very 



oblique to the midrib. 1. A. aureum. 



Petiole unarmed ; venation not very oblique. 2. A. excelsum. 



1. Acrostichum aureum L. Sp. PL 1067. 1753. 



Rootstocks stout, erect, often forming large colonies. Leaves 1-3 m. high; 

 petioles tufted, erect, channelled, often armed with horny spurs; blades leathery 

 in texture, longer than the petioles; pinnae 10 pairs or more, the venation 

 very oblique; sporanges usually borne only on the upper pinnae; segregate of 

 corpuscles covering sporanges not sausage-shaped. 



Wet saline soil, North Cat Cay, Great Bahama, Andros, New Providence, Ack- 

 lin's Island, Caicos, Inagua : Florida ; West Indies. GIANT FERN. LEATHER FERN. 



2. Acrostichum excelsum Maxon, Proc. Biol. Soc. Wash. 18: 224. 1905. 



Acrostichum lomarioides Jenman, Bull. Bot. Dept. Jamaica, 5: 154. 1898. 

 Not Bory, 1853. 



