FLORA OF THE DISTRICT OF COLUMBIA. 57 



1. Filix biilbifera (L.) Underw. 



Shaded talus of cliffs; Virginia side of the Potomac in the region opposite Cabin 

 John; very rare. Newf. to northern Ga., westward. {Cystopteris bulbifera Bernh.) 



2. Filix fragilis (L.) Underw. Brittle pern. 

 Shaded alluvial flats, rocky slopes, and moist woods; abundant in many localities, 



principally along the Potomac; common. Summer, N. Amer. generally; nearly 

 cosmopolitan. {Cystopteris fragilis Bernh.) 



17. DRYOPTERIS Adans. 



Indusia wanting; blades triangular, usually broader than long; pinnae adnate to the 



irregularly winged rachis 1. D. hexagonoptera. 



Indusia present; blades linear-lanceolate or narrowly oblong to ovate, much longer 

 than broad; pinnae sessile, the rachis not winged. 

 Rootstocks very slender, widely creeping, nearly naked; fronds winter-killing, 

 membranous; veins simple or once forked. 

 Lower pinnae gradually decreasing in size, the lowest ones minute. 



2. D. noveboracensis. 

 Lower pinnae scarcely smaller than those above. 



Fertile veins simple 3. D. simulata. 



Fertile veins once forked 4. D- thelypteris. 



Rootstocks stout, short-creeping to erect, conspicuously scaly; fronds mostly ever- 

 green, of firm texture; veins mostly 2 or more timea forked. 

 Blades leathery; sori very much nearer the margins than the midribs of the seg- 

 ments 5. D. marginalis. 



Blades firm, but not thick and leathery; sori about midway from midrib to margin 

 or nearer the midril). 

 Fertile leaves very rigidly erect, tall and slender, long-stalked, the blades 

 linear-oblong to narrowly lanceolate; sterile leaves short, spreading. 



6. D. crista ta. 

 Fertile and sterile leaves mostly ascending or spreading, the blades much 

 broader, mostly oblong to ovate. 



Basal scales thick, shining, dark chestnut-colored 7. D. goldiana. 



Basal scales thin, membranous, dull light brown. 



Pinnae deeply pinnatifid only, the few coarse lobes or divisions all adnate 

 and distinctly joined, the wing very broad toward the tip. 



8. D. clintouiana. 



Pinnae essentially pinnate, at least the basal segments free, the others 



mostly constricted, joined by a faint wing or not. 



Pinnules oblong to oblong-ovate, obtuse or at most acutish.O. D. boottii. 



Pinnules mostly oblong-lanceolate, acute. 



Pinnae oblique to the rachis, the basal ones distant, broadly triangular; 



pinnules obliquely incised, the lobes with curved spinelike teeth; 



indusia without glands 10. D. spinulosa. 



Pinnae at right angles to the rachis, the basal ones ovale, strongly 

 unequal-sided; pinnules pinnately divided, the segments with 

 spreading teeth; indusia glandular 11. D. intermedia. 



1. Dryopteris hexagonoptera (Michx.) C. Chr. Beech fern. 

 Dryish or well-drained open deciduous woods; abundant. Midsummer. Eastern 



N. Amer. {Phegopteris hexagonoptera Y6e.) 



2. Dryopteris noveboracensis (L.) A. Gray. New York fern. 

 Moist low woods and thickets; abundant. July. Eastern N. Amer. (Aspidium 



noveboracense Swartz.) 



