100 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. longimucronata Dav. (P. longimucronata 

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

 Dav. Colorado and Texas to California. 



12. P. densa Hook. Rootstock rather slender, chaffy 

 with blackish 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. (Onych- 

 ium densum Brack.) Utah (Jones), and Wyoming to California, 

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



3. PLATYLOMA J. Sm., Baker. Texture coriaceous, the veins 

 usually hidden, the itltimate segments broad and flat, the indusium 

 so narrow as to be soon hidden by the fruit. 



13. P. Bridges!! Hook. Stipes 2' 6' long, tufted, castane- 

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

 5 1 8 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 Link. Rootstock creeping, rather 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 flexu- 

 osus Kaulf.) Western Texas to California. 



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

 slender, chaffy ; 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- 



