PILICES. (true ferns.) 441 



4. PELLiEA, Link. Cliff-Brake. 



Allied to Cheilanthes, from which it differs chiefly in the continuous invo- 

 lucre and smooth fronds /without tomentum or scales). 



* Fronds herbaceous or sub-coriaceous ; veins dearly visible; involucre broad and 



usually covering the sporangia till they are fully ripe. 



1 • P. Breweri, Eaton. Rootstock short, densely covered with narrow ful- 

 vous chaff: fronds membranaceous, 2 to 6 inches long, simply pinnate with 

 mostly unequally 2-lobed pinnce. — Proc. Am. Acad. vi. 555. From Colorado to 

 Utah and California. In clefts of rocks. 



2. P. gracilis, Hook. Rootstock very slender, creeping, nearly naked: 

 fronds very delicate, 2 to 4 inches long, oblong-ovate, pinnate with a few once 

 or twice pinnatifid pinnce ; segments oblong or obovate ; involucres broad and 

 delicate. — From Colorado northward, eastward through British America, and 

 southward again into Iowa, Pennsylvania, etc. Crevices of damp and shaded 

 limestone rocks. 



* # Fronds subcoriaceous or coriaceous; veins rather obscure; involucre con- 



<- Pinnules obtuse, at least not mucronate : fronds 1 to 2-pinnate. 



3. P. atropurpurea, Fee. Frond 6 to 12 inches long, evergreen, nearly 

 smooth, ovate-lanceolate, usually bipinnate below, simpler upwards ; pinnules 

 oval to linear-oblong, J to 2 inches long. — From Arizona and Alabama 

 northward to British America and Canada. Crevices of shaded limestone 

 rocks. 



•i- 4- Pinnules decidedly acute or mucronate. 



4. p. Wrightiana, Hook. Fronds 4 to 8 inches hag, lanceolate to tri. 

 angular-ovate, bipinnate; pinnae longer than broad, having 3 to 13 oval or 

 oblonq-oval pinnules, fertile ones with the margins rolled in to the midvein. — 

 From Colorado and Arizona to W. Texas. Mostly in exposed rocky places, 

 especially in canons. 



5. P. densa, Hook. Fronds 1$ to 2 inches long, ovate, closely tripinnate ; 

 ultimate segments linear, 3 to 6 lines long, sessile, sterile ones serrated. — In 

 California and Oregon; also at Jackson's Lake, Wyoming (Coulter). Clefts 

 of rocks. 



5. CBYPTOGRAMME, R. Brown. Rock-Brake. 



Fronds rather small, and smooth, 2 to 4-pinnate, the fertile ones taller than 

 the sterile : stalks stramineous and tufted on a short rootstock. 



1. C. acrostichoides, H. Br. Fronds 2 to 4 inches long, chartaceous, 

 ovate, closely 2 to 4-pinnate; pinnules ovate or obovate, adnate-decurrent, 

 those of the fertile fronds narrower and longer, the involucres very broad : sori 

 extending far down the veinlets. — Allosotus acrostichoides, Spreng. From 

 California, Colorado, and Lake Superior, northward to Arctic America. In 

 dense patches among rocks- 



