6 POLYPODIACEAE 



Sori parallel to the midrib or rachis. 



Veins free : sori continuous or nearly so. 14. BLECHNUM. 



Veins anastomosing : sori interrupted, chain-like. 



Leaves uniform : veins free between the sori and the margin. 15. ANCHISTEA. 

 Leaves dimorphous : veins everywhere anastomosing. 19. LORINSERIA. 



Sori wholly or partially oblique to the midrib. 

 Veins free : sori all oblique. 



Sori single on the upper side of a veinlet or rarely crossing it : 



leaf-blades (in our species) not entire. 16. ASPLENIUM. 



Sori confluent in pairs with an apparently double indusium 



opening in the middle : leaf-blades entire. 17. PHYLLITIS. 



Veins united : sori partly parallel to the midrib, partly oblique. 18. CAMPTOSORUS. 

 Sori orbicular or nearly orbicular : indusia less than twice as long as 

 broad. 



a. Indusia superior. 



Sori mostly on the back of the veins. 



Indusia orbicular, peltate, fixed by the center. 



Veins copiously united, forming areolae. 21. TECTARIA. 



Veins free. 22.}PoLYSTicHUM. 



Indusia reniform, or orbicular with a narrow sinus. 23. DRYOPTERIS. 



Sori at the ends of free veins : indusia reniform, opening toward 



the margin of the leaflet. 27. NEPHROLEPIS. 



b. Indusia wholly or partly inferior. 



Indusia partly inferior, delicate, fixed by a broad base, enclosing 



the sorus like a hood. 29. FILIX. 



Indusia wholly inferior, various in shape. 



Indusia cup-shaped or somewhat 2-valved. 28. DENNSTAEDTIA. 



Indusia nearly orbicular or stellate. 30. WOODSIA. 



B. Sporiferous leaf-blades closely rolled together ; segments necklace-like. 



Leaf-blades with anastomosing veins : rootstock horizontal. 20. ONOCLEA. 



Leaf-blades with free veins : rootstock stout, erect. 24. MATTEUCCIA. 



Sporanges spread over 

 Veins forming copious 



1. A. aureum. 



2. A. lomarioides. 



1. ACROSTICHUM L. 



Swamp-inhabiting plants, with the leaves growing in crowns, 

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

 areolae without free veinlets. 



Sporanges formed on the upper leaflets only. 

 Sporanges formed on all the leaflets of some leaves. 



1. Acrostichum aureum L. Rootstocks erect, solitary, or in masses. Petioles 

 tufted, erect, woody, 1-7 dm. long, flattish, channeled, with two or three alternate pairs 

 of black indurated spurs ; 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 : venation fine, oblique to the margin. 



Southern peninsular Florida. Also in tropical regions. 



2. Acrostichum lomarioides Jenman. Rootstocks simitar to those of A. aureum. 

 Petioles tufted, erect, somewhat fleshy, 4-7 dm. long, longitudinally ribbed, slightly an- 

 gular ; blades erect-spreading, 10-12 dm. high, 3-6 dm. wide, slightly reduced at the base, 

 abruptly reduced at the apex ; leaflets spreading, close or crowded, 25-30 pairs, the face 

 turned upward and transverse to the rachis : sporanges covering all the leaflets of fertile 

 leaves : areolae very fine, directed toward the margin. 



Southern peninsular Florida. Also in the West Indies. 



2. POLYPODIUM L. 



Plants with creeping or horizontal rootstocks. Leaves various : petioles jointed to the 

 rootstocks : blades pinnate or simple. Sori hemispheric, dorsal, in one or more rows on 

 either side of the midrib. Indusium none. Veins free or only casually anastomosing. 



Both surfaces of leaf-blades naked. 



Sori large (2 mm. broad): lower segments of the leaf-blade scarcely smaller than the upper. 



1. P. vulgare. 

 Sori smaller (1 mm. wide or less): lower segments of the leaf-blades reduced. 



Leaf-blades with segments 3 mm. wide or less : veins once forked. 2. P. Plumula. 



Leaf-blades with segments 5 mm. wide or more : veins 2-3-forked. 3. P. pectinatum. 



Under surface of leaf-blades with scattered peltate scales. 4. P. polypodioides. 



1. Polypodium vulgare L. Rootstocks widely creeping, densely covered with cinna- 

 mon-colored scales. Leaves evergreen ; petioles light-colored, glabrous, 5-15 cm. long ; 

 blades ovate-oblong or narrowly oblong in outline, slightly leathery, glabrous on both sur- 

 faces, 7-25 cm. long, cut nearly to the rachis into linear or linear-oblong segments : sori 

 borne about midway between the midrib and the margins of the segments. 



On rocks or rocky banks, or rarely on trees, almost throughout eastern North America. Also in 

 Asia and Europe. POLYPODY. 



