lOO OUR NATIVE FERNS AND THEIR ALLIES. 



bipinnate below; pinnae short with i — 2 pairs of long narrow 

 pinnules besides the terminal one; mucro short, with margin 

 broad and cartilaginous ; margins of fertile fronds inflexed to 

 the midrib. Very variable; forms with fronds decreasing to 

 simply pinnate at the apex, and longer but less broadly winged 

 mucro form var. longiiniicionata Dav^ (/*. longijnucroiata 

 Hook.); forms with pinnules densely crowded are var. compacta 

 Dav. Colorado and Texas to California. 



12. P. densa (Brack.) Hook. Rootstock slender, chafTy 

 with blackisli scales; stipes densely tufted, wiry, very slender, 

 castaneous, 3' — 9' long; fronds ovate or triangular- oblong, 

 i' — 3' long, densely tripinnate; segments 3" — 6" long, linear, 

 nearly sessile, sharp pointed or mucronate, in the fertile fronds 

 entire, with the margin narrowly recurved ; in the rare sterile 

 fronds sharply serrate, especially toward the apices. (O/iych- 

 ium densnm Brack.) Utah {Jones), ■awA Wyoming to California, 

 Oregon, and northward ; Mt. Albert, Gaspe, Quebec {Allen). 



§ 3. Platyloma J. Sm., Baker. Texture coriaceous, theveins 

 usually hidden, tJie Jil/iinafe segments broad and fiat, the ittdusium 

 so narro7u as to be soon hidden by the fruit. 



13. P. Bridgesii Hook. Stipes 2' — 6' long, tufted, castane- 

 ous ; fronds 4' — 6' long, i' or more broad, simply pinnate ; pinnae 

 5 — 18 pairs, mainly opposite, nearly sessile, glaucous green, 

 coriaceous, rounded or cordate at the base; indusium narrow, 

 formed of the whitish margin of the pinna, soon flattened out 

 exposing the broad sorus. California. 



14. P. flexuosa (Kaulf.) Link. Rootstock creeping, slender ; 

 stipes reddish, passing into a more or less flexuous or zigzag 

 rachis ; fronds 6' — 30' long, ovate-oblong, bi — tripinnate ; second- 

 ary and tertiary rachises usually deflected and zigzag, rusty 

 puberulent or nearly smooth ; pinnae mostly alternate ; ultimate 

 pinnules 5" — 10" long, roundish-ovate, or sub-cordate, smooth ; 

 margins at first reflexed, soon flattened out. {Allosorus fiexu- 

 osus Kaulf.) Western Texas to California. 



15. P. intermedia Mett. Rootstock long, wide creeping, 

 slender, chafTy ; stipes scattered, 4' — 6' long, pinkish-stramine- 

 ous, smooth; fronds 5' — 10' long, 3' — 8' wide, ovate-bipinnate ; 

 pinnae nearly opposite, remote ; pinnules 2 — 6 pairs, petiolate, 

 sub-coriaceous, oval or cordate-ovate ; veins obscure ; ra- 



