!040 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, above ground. 



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

 Veins of the sterile fronds netted. 1. ONOCLEA. 



Veins of the sterile fronds free. 2. PTERETIS. 



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



Sori on the under surface of the fronds, each provided with a special indusium not 



connected with the margin of the frond. 

 Sori roundish. 



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



Indusia inferior, stellate or split into spreading lobes. 3. WOODSIA. 

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



finally thrown back or evanescent. 4. FILEX. 



Indusia superior. 



Indusia peltate. 5. POLYSTICHUM. 



Indusia orbicular-reniform, adherent at the sinus. 



Mid veins and midribs united at a wide angle; fronds usually provided 

 with true hairs, consisting of a single cell or a single row of cells. 



6. THELYPTERIS. 

 Midveins and midrib united at a very acute angle; fronds lacking true 



hairs. 7. DRYOPTERIS. 



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



Sori all straight or rarely slightly curved, single on the sides of the veins. 



8. ASPLENIUM. 

 Sori, at least in part, shaped like 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. NOTHOLAENA. 



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



Stipes jointed to the rhizome. 15. POLYPODIUM. 



Stipes not jointed to the rhizome. 6. THELYPTERIS. 



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. ADIANTUM. 

 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 connecting the ends of the 



veinlets. 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 alike 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 FERN. 



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

 Ue fronds foliaceous. Fertile fronds with rigid, contracted bail-like subdivisions, 

 ban roundish on elevated receptacles, partly covered by delicate hood-like indusia 

 attached to the bases of the receptacles. 



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



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



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



