Flora of the Palouse Region 



Sori dorsal or marginal, provided with special indusia. 



Sori roundish; indusia less than twice as long as broad. 



Veins of pinnules pinnately branched. 3. Woodsia. 



Veins of pinnules dichotomously branched. 4. CystopTERIS. 



Sori linear or oblong; indusium more than twice as long as broad. 



7. Asplenium. 

 vSori with marginal indusia formed of the more or less altered edge of the leaf. 

 Sporangia on a continuous vein-like receptacle which connects the ends 



of the veins. 5. PTERIS. 



Sporangia at or near the ends of unconnected veins. 6. CheilanThes. 

 Sori without indusia, roundish. 8. PheoopTERIS. 



3. WOODSIA. 



Small or medium sized ferns, growing in rocky places: leaves 

 1-2 pinnate or pinnatifid: sori round, borne on the backs of pin- 

 nately forked free veins; indusium attached all around the recep- 

 tacle underneath the sporangia, early bursting at the top into 

 irregular pieces or lobes, and, when mature, usually concealed by 

 the sorus. 



W. Oregaiia D. C. Eaton. Rootstock short: petioles glabrous, not jointed, 

 brownish below; blades slightly roughened, 5-28 cm. long, elliptic-lanceolate, 

 the sterile shorter than the fertile; pinnae triangular-oblong, obtuse, pin- 

 natifid; lower pinnae reduced in size and somewhat remote from the others; 

 rachis straw-colored; segments oblong or ovate, dentate or crenate, teeth 

 often reflexed and covering the sori. Common in crevices in rocks, usually 

 in shady places, Pullman. 



4. CYSTOPTERIS. 



Delicate rock-ferns: leaves 24 pinnate; leaf-stalks slender: sori 

 round, borne on the backs of dichotomously branched free veins 

 (in ours); indusium attached partly under the sorus on the side 

 toward the midvein, early opening and withering away. 



C. fragilis Bernh. Rootstock short: petioles 10-20 cm. long; blades thin, 

 oblong-lanceolate, only slightly tapering below, 10-25 cm. long, 3-7 cm. 

 wide, 2-3 pinnatifid or pinnate; pinnae lanceolate-ovate, irregularly pin- 

 natifid with bluntly or sharply-toothed segments along the margined or 

 winged rachis; texture membranous. Not very common; shady woods, 

 Thatuna Hills. 



5. PTERIS. 



Large, mostly coarse ferns, with variously divided, or, in trop- 

 ical species, simple leaves, and marginal linear continuous sori 

 which occupy a slender thread-like receptacle connecting the tips 

 of free veins; indusium membranous, formed of the reflexed mar- 

 gin of the leaf: leaf-stalks continuous with the rootstock. 



P. aquilina L, Rootstock stout, black, subterranean, horizontally-creep- 

 ing: petioles 30-90 cm. high, erect, pale-green or straw-color; leaf-blades 

 60-120 cm. long, 30-90 cm. wide, glabrous or nearly so, ternate, the three 



