1040 POLYPODIACEAE 



segments, and with broader rhomboid tips, the segments crenulate; panicle of 

 the sporophyll diffuse. Fields and open woods: Ont. — Que. — N.J. — Pa. — Wis.; 

 Alaska — B.C. — Calif. Submont. — Mont. 



Family 2. POLYPODIACEAE. Fern Family. 



Sporophytes consisting of a rhizome and leaves (fronds) coiled in the bud. 

 Sterile fronds leaf-like, fertile fronds (sporophylls) either leaf-like or par- 

 tially or completely non-foliaceous, bearing the sporanges on their lower sur- 

 face or at their margins, commonly in clusters (sori). Sori naked or fur- 

 nished with a special covering (indusium). Sporanges stalked, furnished 

 with an incomplete vertical ring of thickened cells (annulus), opening trans- 

 versely. Prothallia green, al)ove ground. 



Fertile fronds, with contracted berry-like or necklace-Uke subdivisions, not foliaceous. 

 Veins of the sterile fronds netted. 1. Oxoclea. 



Veins of the sterile fronds free. 2. Pteretis. 



Fertile and sterile fronds foUaceous, alike or differing; veins free. 



Sori on the under siu-face of the fronds, each provided with a special indusium not 

 connected -with the margia of tlie frond. 

 Sori roundish. 



Indusia inferior or attached at base at one side of the sorus. 



Indusia mferior, stellate or spht into spreading lobes. 3. WooDSi.\. 

 Indusia attached at base at one side of tlie sorus, at first arched over it, 

 finally thi'own back or evanescent. 4. Filex. 



Indusia superior. 



Indusia peltate. 5. POLYSTICHUM. 



Indusia orbicular-reniform, adherent at the sinus. 



Mid veins and midribs miited at a wide angle: fronds usually provided 

 with true hau-s, consisting of a single cell or a smgle row of cells. 



6. Thelypteris. 

 Mid veins and midrib miited at a very acute angle; fronds lacking true 

 hairs. 7. Dkyopteris. 



Sori oblong or linear, or shaped Uke a horseshoe or shepherd's crook. 



Sori all straight or rarely sUghtly curved, smgle on the sides of the veins. 



8. ASPLENIUM. 



Sori, at least m part, shaped hke a horseshoe or shepherd s crook, crossing the 

 fertile vein and more or less recurved upon it. 9. Athyrium. 



Sori naked, or protected, at least at first, by the revolute or reflexed margins or por- 

 tions of the margins of the frond. 

 Margin of the frond flat or merely revolute, not modified. 



Margin of the frond revolute; sori more or less confluent, forming a marginal 



band. 16. Nothol.\e.va. 



Margin of the frond flat; sori dot-Uke on the veins. 



Stipes jomted to the rliizome. 15. Polypodium. 



Stipes not jointed to the rhizome. 6. Theia'PTERIS. 



^Margin of the frond reflexed over the sori, more or less modified. 



Sori borne on the under side of reflexed lobes of the frond. 10. AmAXTtnw. 

 Sori not borne on the under side of the reflexed portions of the margin of the 

 frond. , , ... 



Sori borne on a continuous vein-like receptacle connectmg the ends of the 



vemlets. 11- Pteris. 



Sori borne on the veins at or near their tips. 



Sori extending down the veins: edges of the fertile fronds finally open- 

 ing out flat; sterile and fertile fronds markedly dissimilar. 



12. Cryptogramma. 

 Sori marginal or submarginal; sterile and fertile fronds aUke or some- 

 what dissimilar. 

 Sori confluent, forming a submarginal band; segments of the fronds 



glabrous or nearly so. 13. Pellaea. 



Sori distinct or contiguous; segments usually pubescent, tomentose 

 or scaly. 14. Cheilanthes. 



1. ONOCLEA L. Sensitive Fekn. 



Ferns, with coarse dimorphous fronds scattered on creeping rhizomes. Ster- 

 ile fronds foliaceous. Fertile fronds with rigid, contracted ball-like subdivisions. 

 Sori roundish, on elevated receptacles, partly covered by deUcate hood-like indusia 

 attached to the bases of the receptacles. 



1. O. sensibilis L. Sterile fronds 3-13.5 dm. high, deltoid-ovate, pinnat- 

 ifid; segments lanceolate-oblong, entire, undulate or sinuate-pinnatifid; rachis 

 winged; veins anastomosing; fertile fronds 3-7.5 dm. high, bipinnate; pinnules 



