94 Slender Cliff-Brake 



short-stalked, the upper sessile and decurrent: sporophylls com- 

 monly more deeply cut than sterile leaves: ultimate segments 

 adnate-decurrent, the inferior mostly longer than the superior; 

 fertile segments lanceolate or linear-oblong on the smaller oval 

 or roundish, obtuse or appearing acute or subacute from the re- 

 flexed margins; the apical mostly the longest; sterile segments 

 obovate or ovate or roundish, crenately toothed or lobed, obtuse : 

 rachis greenish or below brown, grooved on face: surfaces gla- 

 brous: color pale green: texture thin, membranous. 



Venation conspicuous, pinnate, free: primary branches of 

 midveins of fertile segments simple to twice-forked or rarely bear- 

 ing several simple or once-forked branches, commonly simple or 

 once-forked: primary branches of midveins of sterile segments 

 varying as in fertile segments, the average more complex than 

 average of latter: midveins sometimes not evident in small seg- 

 ments. 



Sori clustered on upper part of veins: indusia consisting of 

 reflexed altered margin of segments, extending along sides and 

 often around apices of segments or in segments bearing few scat- 

 tered sori sometimes present only at soriferous points, at length 

 opening out more or less flat, delicately membranaceous, the 

 margin more or less erose or minutely denticulate or entire. 



Spores spheroid-tetrahedral, obscurely trivittate. 



Habitat. Clefts and ledges of shaded moist calcareous rock, 

 or on sandstone, mica-schist, or gneissoid rock;* particularly 

 near streams and lakes in cold mountain glens and ravines. 



Range. Labrador to Alaska, south to Massachusetts, Penn- 

 sylvania, Illinois, Iowa, and in the Rocky Mountains to Colo- 

 rado. 



* See Fern Bull. 10 :$6. 1902. Also Torreya, 2: 176. 1902. 



