FILICES. 109 



2. P. hexagonoptera (Michx.) Fee. Stipes stramineous, 

 naked; fronds as broad as long or nearly so, 7' — 12' long, 

 slightly pubescent, and often finely glandular beneath; upper 

 pinnae oblong, obtuse, toothed or entire, the very large, lowest 

 pinnae elongate and pinnately lobed ; sori near the margin or 

 some between the sinus and the midrib. {Polypodimn hexagott- 

 optcrum Michx.) Canada to Illinois, Kentucky, and Florida. 



** Fronds oblong-lanceolate, tripinnatifid ; rachis wingless. 



3. P. alpestris (Hoppe) Mett. Rootstock short, erect or 

 oblique; stipes 4' — 10' long, with a few brown spreading scales 

 near the base ; fronds 1° — 2° long, pinnae deltoid-lanceolate, the 

 lower ones distant and decreasing moderately ; pinnules oblong- 

 lanceolate, incised and toothed ; sori small, rounded, sub- 

 marginal. {Polypodium alpestre Hoppe, Aspidium alpestre 

 Swz.) California and northward ; Idaho {Sandberg). 



*** Fronds fcrnate, I he three divisions petioled ; rachis wingless. 



4. P. dryopteris(L.) Fee. (Oak-fern.) Rootstock slender, 

 creeping; fronds bnjadly triangular, 4' — 8' wide; the tliree 

 primary divisions i— 2-pin nate ; segments oblong, obtuse, entire 

 or toothed ; sori near the margin. {Polypodium dryoptcris L., 

 Niphrodimn dryoptcris Michx.) Northeastern United States to 

 Virginia, and westward to Oregon and Alaska. 



Var. Robertianum (Hoffm.) Dav. Stipes 6'— 10' long, 

 stramineous, glandular ; fronds 6'— 8' long, 5'— 7' wide, deltoid- 

 ovate in outline, bipinnate, lowest pair of pinnae far the largest, 

 pinnatifid or again pinnate; upper pinnae smaller, pinnatifid, 

 Iobcd,or entire ; sori copious, forming submarginal rows around 

 the segments. {P. calcarea Fee.) Minnesota {Cathcart), Deco- 

 rah, Iowa {Hohuay), Northeast Territory {Macoun), Idaho. 



§ 2. GoNlOPTERlS Presl. Veins pinnate, the loiucr veinleis 

 of contiguous gro7ips tmiting. 



5. P. tetragona (Swz.) Fee. Rootstock creeping ; stipes 

 6' — 18' long, naked or slightly villose ; fronds 1° — 1° long, 

 6' — 1 2' broad; pinnae numerous, spreading 3' — 6' long, the lowest 

 narrowed at the base and sometimes stalked, deeply pinnatifid ; 

 texture thinly herbaceous; rachis and under surface finely 

 pubescent ; sori in rows near the midrib. Marion County, 

 Florida {Reynolds). ^ 



