1048 POLYPODIACEAE 



margins slightly hairy; surfaces otherwise glabrous or with a few scattered hairs; 

 hairs mostly pluricellular. Rare in the west, where it is replaced by the following 

 variety. Woods: Newf.—Fla.— Colo. (?)— S.D.;Eu. Subinont. —Mont— Boreal. 

 Pterin aquilina puhesretts Kuntzc. Pinnules more regularly pinnatifid, the 

 entire ones often deltoid-oblong; midribs only slightly raised, not broad and 

 conspicuously elevated; under surface pubescent or tomentose, the upper slightly 

 hairy or glabrous; hairs slender, many, short, erect, setiform or hamate and uni- 

 celliilar, others longer, often tortuous and pluricellular. Pteridium aquilina 

 pubescens Underw. Pien's Feei Schaff ner. Woods: Alaska — Mont. — N.M. — Cal- 

 if.; Mex., Guatemala, and (?) Eu. 



12. CRYPTOGRAMMA R. Br. Rock-brake. 



Small ferns, with slightly dimorphous compound fronds. Margins of the 

 blades' subdivisions reflexed over the sporangia, finally opening out flat. Spor- 

 angia without other indusia, on the upper part of the veins and extending down 

 them. Veins free. 



Fronds scattered; leaf-texture very delicate; stipes brown or brownish below or through- 

 out. 1. C. StcUeri. 



Fronds tufted; leaf-texture firm. 



Stipes straw-colored. 2. C. acrostichoidcs. 



Stipes chestnut-colored. 3. C. densa. 



1. C. Stelleri (Gmel.) Prantl. Rhizome slender, creeping; fertile fronds 

 5.5-22 cm. long, the sterile usually shorter; blades ovate, bi-tripinnatifid ; ulti- 

 mate segments cuneate and decurrent at base, the fertile linear-oblong to lance- 

 hnear, the sterile ovate to obovate-flabelliform, crenulate. Pellaca gracilis Hook. 

 On shaded, damp, mostly limestone, rock: Que. — Ga. — Minn. — Sask. — Mont. — 

 B.C.; Colo.; India. Suhnont. — Mont. 



2. C. acrostichoides R. Br. Feitile fronds 8-36 cm. long, long-stalked, 

 commonly overtopping the sterile; blades ovate, the sterile tri-quadripinnatifid; 

 sterile ultimate segments ovate-oblong or suboval, obtuse, serrulate, the fertile 

 narrowly elhptical or linear, their reflexed margins scarcely altered. On rocks: 

 Baffin Bay — Mont. — Sask. — Colo. — Calif. — Alaska. Submoni. — Subalp. 



3. C. densa (Brack.) Diels. Prunary rachis, except in the upper part of the 

 blade, and scales of rhizome chestnut-colored, like the stijje; fronds 6-29 cm. 

 long; blades ovate or oblong-deltoid, densely tripinnate; sterile ultimate segments 

 lance-linear, incisely serrate, the fertile linear, nearly sessile, their reflexed mar- 

 gins delicately indusiform, erose-toothed. Pellaea densa Hook. On rocks: 

 B.C.— Mont.— N.M.— Utah— Calif.; se Canada. 



13. PELLAEA Link. Cliff-brake. 



Ferns, with compoimd fronds and usually dark-colored stipes, the fertile 

 divisions usually narrower than the sterile. Sori borne on the upper part of the 

 free veins, ususlly confluent in a submarginal Hne. Margins of the fertile seg- 

 ments reflexed over the sporangia, indusiform. 



Segments of the blade obtuse or acute, rarely a few mucronate. 



Blades once pinnate, the pinnae mostly two-parted; stipes repeatedly marked with 



transverse crack-like depressions. 1. P- Brrwvri. 



Blades once or twice pinnate; stipes not marked with transverse depressions. 



Stipes and racliises reddish brown, entirely glabrous or with only few occasional 



long flaccid jointed hairs. 2. P. (jlahrlla. 



Stipe and racliises purplisli black, rather thickly clothed with slender flaccid 

 jointed hairs. 3. P. atropurpurca. 



Segments sliarp-pointed or mucronate; blades once pinnate above, bipinnate below. 



4. P. mucronata. 



1. P. Breweri D. C. Flat. Scales of rhizome rust-colored; fronds tufted, 

 5-20 cm. long; stipes brittle, breaking off above the scales, reddish brown; 

 rachis reddish brown except near apex; blades oblong; pinnae short-stalked, the 

 superior segment the larger, segments obtuse or the fertile subacute; indusia 

 pale. On rocks: Ida. — Calif. 



