GROUP III 



FERTILE FRONDS UNIFORMLY SOMEWHAT LEAF-LIKE IN 



APPEARANCE, YET DIFFERING NOTICEABLY FROM 



STERILE FRONDS 



t5. SLENDER CLIFF BRAKE 



Pellaa gracilis {P. Stelleri) 



Labrador to Pennsylvania, usually on sheltered rocks, preferring 

 limestone. Two to five inches long, with straw-colored or pale- 

 brown stalks, slightly chaffy below. 



Fronds. — Delicate, with few pinnae ; pinna, the lower ones once 

 or twice parted into 3-5 divisions, those of the fertile frond 

 oblong or linear-oblong, sparingly incised, of the sterile frond ovate 

 or obovate, toothed or incised ; sporangia bordering the pinnas o( 

 the fertile frond, covered by a broad and usually continuous gen- 

 eral indusium, formed by the reflexed margin of tiie pinnule. 



The first time I found the Slender Cliff Brake 

 was one July day in Central New York, under the 

 kind guidance of an enthusiastic fern collector. A 

 rather perilous climb along the sides of a thickly 

 wooded glen brought us to a spot where our only 

 security lay in clinging to the trees, which, like our- 



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