POLYTODIACE^.. 97 



ly covered with white powder; sori numerous, very small. 



Alaska. 



XIV. CRYPTOGRAMMA R. Br. ROCK BRAKE. 



Sporangia on the back or near the ends of the free veins, 

 forming oblong or roundish sori, which are at length confluent, 

 and cover the back of the pinnules. Indusium continuous, 

 formed of the membranous, somewhat altered margin of the 

 pinnule, at first reflexed along the two sides and meeting at the 

 midrib, at length opening out flat. Name from Gr. KpvTtroS, 

 concealed, and ypdn^a, line, alluding to the concealed fructifi- 

 cation. A boreal genus of three species. 



1. C. acrostichoides R. Br. Stipes densely tufted, stra- 

 mineous; fronds dimorphous, sterile ones on shorter stalks, 

 tri quadripinnatifid, with toothed or incised segments; fertile 

 ones long-stalked, less compound, with narrowly elliptical or 

 oblong-linear pod-like segments. (C. crispa, forma Americana 

 Hook., Allosorus acrostichoides Spreng.) Lake Superior, Colo- 

 rado to California and northward. 



2. C. Stelleri (Gin.) Prantl. Stipes scattered, 2' 3' long, 

 stramineous or pale-brown; fronds 2' 4' long, i' 2' broad, 

 ovate, bi tripinnatifid ; pinnae lanceolate-deltoid, cut to the 

 rachis into a few broad, blunt, slightly lobed pinnules ; texture 

 thinly herbaceous, flaccid ; indusium broad, continuous, mem- 

 branous; veins of the fertile fronds mostly only once forked. 

 (Pell<za gracilis Beddome and former edition, A. gracilis Presl, 

 Pteris gracilis Michx., P. Stelleri Gmelin.) Labrador to 

 Pennsylvania, Illinois, Colorado, and northward. 



XV. PELL^EA Link. CLIFF-BRAKE. 



Sori intramarginal, terminal on the veins, at first dot-like or 

 decurrent on the veins, at length confluent laterally, forming a 

 marginal line. Indusium commonly broad and membranous, 

 formed of the reflexed margin of the fertile segment. Name 

 from Gr. jreAAoS, dusky, alluding to the dark-colored stipes. In- 

 cludes 55 species. 



i. CHEILOPLECTON Fee, Baker. Texture herbaceous or sub- 

 coriaceous, veins clearly visible, indusium broad, in most of the 

 species rolled over the sorus till maturity. 



