416 



POLYPODIACEAE. 



coiled in vernation. Sporanges borne in clusters (sori) on the lower side 

 or margins of the leaves or their segments, stalked, provided with a vertical 

 ring 1 , opening transversely. Sori with or without a membranous covering 

 (indusium). Prothallium green. About 150 genera and 4500 species of 

 wide distribution. 



Sori confluent, covering the under sides of leaf-segments. 

 Sori separated, not covering leaf-segments. 

 Sori without indusia. 

 Sori with indusia. 

 Indusia marginal. 



Sporanges on continuous, vein-like receptacles. 

 Indusia simple. 



Stipe of leaf with one fibrovascular bundle. 

 Stipe with more than one fibrovascular bundle. 

 Indusia double. 



Sporanges at the ends of veins. 

 Indusia dorsal. 



Sori twice as long as wide or longer. 

 Sori parallel to the midvein. 

 Sori oblique to the midvein. 

 Indusia mostly simple. 

 Indusia commonly double. 

 Sori orbicular or nearly so, or reuiform. 

 Sori borne on the backs of veinlets. 

 Indusia orbicular, peltate. 

 Indusia reniform. 

 Sori borne at the ends of veinlets. 



1. Acrostichum. 



2. Poly-podium. 



3. Pycnodoria. 



4. Anopteris. 



5. Ptcris. 



6. Adiantum. 



7. Anchisteu. 



8. Asplenium. 



9. Diplazium. 



10. Polystichum. 



11. Dryopteris. 



12. Nephrolepis. 



1. ACROSTICHUM L. 



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

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

 ments. Veins forming copious areolae without free veinlets. [Greek, signify- 

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

 America. Type species: Acrostichum aureum L. 



1. Acrostichum excelsum 



Maxon. GIANT FERN. (Fig. 451.) 

 Rootstocks erect, solitary, or in 

 masses. Petioles tufted, erect, 

 woody, 4'-27' long, flattish, chan- 

 neled ; blades leathery, 3-4 long, 

 l-li wide; segments 10 pairs or 

 more, rather distant ; sporanges 

 confined to the upper half or third 

 of the leaf-blade, or all segments 

 spore-bearing, or all without spores ; 

 segregate of corpuscles covering 

 sporanges sausage-shaped; vena- 

 tion fine, oblique to the margin. 

 [A. aureum of Eeade, Hemsley, 

 Jones and Lefroy; A. lomarioides 

 Jenman, not Bory.] 



Common in marshes. Native. 

 Florida and the West Indies. Small 

 plants have been referred to the 

 tropical American A. aureum L., 

 which differs in having star-shaped 

 segregates of the corpuscles covering 

 the sporanges. 



