POLYPODIACEAE 



Plants with very narrow grass-like blades; veins obscure, 



the areoles in a single row, without included veinlets. 6. VITTARIA. 

 Plants with shorter broader blades; veins freely anas- 

 tomosing, the areoles with included veinlets. 7. PALTONIUM. 

 Sori with indusia (or these vestigial or wanting in some species of No. 26) . 

 Indusia formed in part of the more or less modified leaf-margin: sori 



essentially marginal. 

 Sporanges borne within cup-shaped or pocket-like indusia. 



Leaves numerous, tufted; indusia flattish, pocket-like, 



partly joined to the similar opposed leaf-lobe. 30. SPHENOMERIS. 



Leaves few, not tufted; indusium truly cup-shaped. 31. DENNSTAEDTIA. 



Sporanges not borne within cup-shaped or pocket-like indusia. 

 Sporanges borne on a continuous vein-like receptacle connect- 

 ing the apices of the veins. 



Indusium single, formed of the altered leaf-margin. 8. PTERIS. 



Indusium double, an inner membranous portion arising 



from the receptacle. 9. PTERIDIUM. 



Sporanges borne at or near the apices of the unconnected 



veins. 

 Lobes of the leaf-margin bent back only over the sori, 



as indusia. 



Petioles dark, wiry, polished. 10. ADIANTUM. 



Petioles yellowish to brown, stouter, not polished. 13. HYPOLEPIS. 



Leaf-margins wholly reyolute orreflexed in fertile leaflets. 



Sori confluent, forming a wide submarginal band. 11. PELLAEA. 



Sori usually distinct, if confluent the segments small. 12. CHEILANTHES. 

 Indusia not formed in part of the leaf-margin; sori not marginal 

 Sori mostly linear to oblong; indusia more than twice as long as 



broad. 

 Sori parallel to the midrib or rachis. 



Veins free: sori continuous or nearly so. 15. BLECHNUM. 



Veins anastomosing: sori interrupted, chain-like. 



Leaves uniform: veins free between the sori and the 



margin. 16. ANCHISTEA. 



Leaves dimorphous: veins freely areolate. 22. LORINSERIA. 



Sori wholly or partially oblique to the midrib. 

 Veins free: sori all oblique. 



Sori confluent in pairs: indusia single but contiguous. 19. PHYLLITIS. 

 Sori single on the outer side of the yeinlet, or crossing it. 



Leaves mostly evergreen: sori usually straight. 17. ASPLENIUM. 



Leaves herbaceous or membranous:* sori usually 



curved, often crossing the veinlet and recurved. 18. ATHYRIUM. 

 Veins copiously anastomosing: sori variously disposed. 20. CAMPTOSORUS. 

 Sori roundish: indusia less than twice as long as broad. 

 Indusia (if present) superior, reniform to orbicular. 



Leaflets articulate, deciduous: sori terminal. 29. NEPHROLEPIS. 



Leaflets not articulate, persistent: sori mostly on the 



backs of the veins. 



Veins copiously anastomosing, the areoles irregular. 24. TECTARIA. 

 Veins free, or, if the lower pairs joined, these forming 



regular areoles. 

 Indusia orbicular, centrally attached: plants rigid, 



the leafy parts mostly spinulose or mucronate. 25. POLYSTICHUM. 

 Indusia (if present) reniform, or orbicular with a 

 narrow sinus: plants more delicate, the leaf- 

 segments usually not spinulose. 26. DRYOPTERIS 

 Indusia wholly or partly inferior, hood-shaped or stellate. 

 Indusium wholly inferior, the divisions spreading, 



stellate or hair-like. 33. WOODSIA. 



Indusium hood-shaped, attached by its base at one side 



of the sorus, withering. 32. FILIX. 



B. Fertile leaf-blades with the ultimate divisions closely rolled together, 

 ^J brownish, necklace-like or berry-like. 



Sterile blades deeply pinnatifid: veins,, freely anstomosing. 23. ONOCLEA. 



Sterile blades deeply 2-pinnatifid: veins free. 28. MATTEUCCIA. 



1. ACROSTICHUM L. 



Swamp-inhabiting plants, with the leaves growing in crowns. Sporanges spread 

 over the whole lower surface of the leaf -blades, or of the upper leaflets. Veins 

 forming copious minute areolae without free veinlets. 



Sporanges borne on the upper leaflets: petioles relatively slender, nearly terete. 1. A. aureum. 

 Sporanges covering all the leaflets of some leaves: petioles stout, channeled. 2. A. excelsum. 



1. Acrostichum aureum L. Petioles tufted, erect, 1-7 dm. long; blades stiff, 

 leathery, glossy, light green, 10-12 dm. long, 3-4 dm. wide; leaflets 12 pairs or more, 

 rather distant: sporanges confined to the upper half or third of the leaf -blade. 



Southern peninsular Florida. Also in tropical regions. 



2. Acrostichum exce"lsum Maxon. Petioles tufted, erect, 4-5 dm. long; blades 

 erect-spreading, 10-16 dm. high, 3-7.5 dm. wide, slightly reduced at the base, abruptly 



