. PTERIDOPHYTA. I/ 



3. Phegopteris Dryopteris (L.) Fee. OAK-FERN. (I. F. 41.) Rootstock 

 creeping. Stipes slender, 1-3 dm. long, chaffy at least near the base ; leaves thin, 

 broadly triangular, almost glabrous, 1-2 dm. wide, ternate, the three primary 

 divisions stalked, pinnate or partly bipinnate, the terminal one slightly larger, 

 all spreading more or less at right angles to the stipe ; pinnules lanceolate or ob- 

 long-lanceolate, obtuse to subacute, sessile ; segments oblong, obtuse, entire or 

 crenate, close together. In moist woods and swamps, Newf. to Alaska, south to 

 Va., Minn., Or., and in the Rocky Mts. to Colo. Also in Europe and Asia. 



4. Phegopteris Robertiana (Hoffm.) A. Braun. Stipes 15-25 cm. long, 

 straw-colored when dry ; leaves 8-20 cm. long, mostly erect, 12-18 cm. wide, del- 

 toid-ovate, bipinnate, the lowest pinnae much the largest, pinnatifid or again pinnate; 

 upper pinnae smaller, pinnatifid, lobed or entire; sori numerous. Lab. to la. and 

 Idaho. Also in Europe. (Phegopteris Dryopteris Robertiana Davenp.) 



15. FfLIX Adans, 1763. {Cystopteris Bernh. 1806.] 



Delicate rock ferns with slender stipes, 2-4-pinnate leaves, and roundish sori 

 borne on the backs of the veins. Indusium membranous, hood-like, attached by a 

 broad base on its inner side and partly under the sorus, early opening and some- 

 what evanescent. Veins free. Sporanges pedicelled, provided with a transversely 

 bursting vertical ring. [Ancient name of the fern plant. ] Five species, natives of 

 the north temperate zone. 



Leaves ovate-lanceolate or lanceolate, 2-3-pinnate. 



Leaves broadest at base, long-tapering, bearing bulblets beneath. i. F. bulbifera. 



Leaves scarcely broader at base, short- pointed ; no bulblets. 2. F.fragilis. 



Leaves deltoid-ovate, 3-4-pinnate. 3. F, montana. 



1. Filix bulbifera (L.) Underw. (I. F. f. 23.) Rootstock short, rooting. 

 Stipes 10-15 cm - l n g light-colored; leaves elongated, lanceolate from a broad base, 

 38 dm. long, 2 3-pinnatifid or pinnate ; pinnules crowded, toothed or pinnatifid ; 

 rachis wingless, commonly bearing underneath , in the axils of the pinnae and seg- 

 ments, large fleshy bulblets which fall away and propagate the plant ; indusia short, 

 truncate on the free side, early thrown back and withering. On moist rocks, espe- 

 cially limestone, Quebec to Wis., south to Tenn. and Ark. 



2. Filix fragilis (L.) Underw. (I. F. f. 24.) Rootstock short. Stipes 10-20 

 cm. long; leaves thin, oblong-lanceolate, slightly tapering below, 1-3 dm. long, 2-3. 

 pinnatifid or pinnate ; pinnae lanceolate-ovate, irregularly pinnatifid, with a broad 

 central space and bluntly or sharply toothed segments decurrent along the mar- 

 gined or winged rachis, without bulblets ; indusia narrow or acute at the free end, 

 early withering ; texture membranous. On rocks and in moist grassy woods, Newf. 

 to Alaska, south to Ga. and Ariz. Almost cosmopolitan. 



3. Filix montana (Lam.) Underw. (I. F. f. 25.) Rootstock widely creeping. 

 Stipes 15-22 cm. long, slender; leaves deltoid-ovate, 3-4-pinnate, about 15 cm. long 

 and broad, the lowest pinnae deltoid-lanceolate and much larger than the upper, 

 their inferior pinnules 2.5-3 cm. long ; segments deeply divided into oblong lobes, 

 deeply toothed ; sori numerous ; indusia acute, soon withering. On rocks, Lab. 

 and Quebec to Br. Col., south to the north shore of L. Superior, and Colo. Also 

 in N. Europe and Asia. 



16. WOODSIA R. Br. 



Small or medium-sized ferns, growing in rocky places, with i-2-pinnate or 

 pinnatifid leaves and round sori borne on the backs of simply forked free veins. 

 Indusia inferior^ thin and often evanescent, roundish or stellate, either small and 

 open or early bursting at the top into irregular lobes or segments. Stipes often 

 jointed above the base and separating at the joint. [Name in honor of Joseph 

 Woods, 1776-1864, English architect and botanist.] About 15 species, natives of 

 temperate and cold regions. 



Indusium minute or evanescent, flat, concealed beneath the sorus, its margin cleft into 

 slender hair-like segments. 



