28 Karl M. Wiegaistd and Arthur J. Eames 



2. C. fragilis (L.) Bernh. Bladder Fern. 



Damp or rather dry shaded cliffs and banks, in somewhat calcareous or even sub- 

 acid gravels and shales ; less common than the preceding. June 10-Aug. 10. 



In nearly all the ravines of the basin, also in steep rocky hillside woods. 



Newf. and Lab. to Alaska, southw. to Ga., Ala., Kans., Ariz., and s. Calif., includ- 

 ing the Atlantic Coastal Plain. Almost cosmopolitan. 



3. Pteretis Raf. 

 1. P. nodulosa (Michx.) Nieuwl. (Onoclca Struthiopteris of authors.) Ostrich 

 Fern. 



Open alluvial slightly acid or slightly calcareous soil, especially on the flood plains 

 of streams ; frequent. Sept.-Oct. 



Key Hill swamp; Inlet, near Lick Brook; Negundo Woods; Etna; Fall Creek, e. 

 of Freeville ; Isoetes Pond, Cortland marl ponds; Salmon Creek, s. of Genoa; Paine 

 Creek; Big Gully Point. 



Newf. to B. C., southw. to Va. and Iowa; rare or absent on the Atlantic Coastal 

 Plain. 



Slender stolons produce new clumps of fronds. 



4. Onoclea L. 

 1. O. sensibilis L. Sensitive Fern. 



Low meadows and thickets, in slightly calcareous or slightly acid soils; common, 

 and generally distributed. Sept.-Oct. 



Newf. to Sask., southw. to Fla. and Okla., including the Coastal Plain. Found 

 also in e. Asia. 



5. Thelypteris Schmidel 

 a. Indusium wanting; rootstocks creeping; fronds easily killed by the frost. 



b. Basal pinnae stalked, rhachis of the frond not winged; blade nearly horizontal, 



subternate ; veins simple or once forked. 1. T. Dryopteris 



b. Basal pinnae sessile or partly adnate, the rhachis more or less winged ; blades 

 suberect, not ternate. 

 c. Fronds usually broader than long, finely puberulent or glandular beneath, or 

 with a few white scales along the veins ; rhachis above the lowest pair of pin- 

 nae winged ; these pinnae 2.5-7 cm. wide, in the same plane as the rest of the 

 blade ; pinnules of the lowest pinnae longer than in the next species, and 

 often pinnatifid ; veins of the pinnules on the lowest pair of pinnae several 

 times forked. 2. T. hexagonoptera 



c. Fronds longer than broad, more coarsely pubescent beneath and with prominent 

 brown scales along the veins ; rhachis above the lowest pair of pinnae prac- 

 tically wingless ; these pinnae 1.5-2.5 cm. wide, bent upward, perpendicular to 

 the leaf surface ; veins simple or once forked. 3. T. Phegopteris 



a. Indusium present, horseshoe-shaped or reniform. 



b. Rootstocks creeping; veins simple or once forked; fronds easily killed by the 

 frost, often pubescent. 

 c . Lowest pinnae scarcely smaller than the middle ones ; fronds ovate or narrowly 

 ovate, truncate at base, long-stalked; margins of the fertile pinnules revolute ; 

 veins forked ; indusium glandless. 4. T. palustris 



c. Lowest pinnae smaller than the middle ones ; fronds tapering both ways from 

 the middle ; margins of the fertile pinnules flat ; veins simple ; indusium 

 glandular. 5. T. novcburaccnsis 



b. Rootstocks short, suberect; veins, at least the lowest, more than once forked; 

 fronds cespitose, evergreen or subevergreen, never pubescent. 

 c. Fronds 2-pinnatifid or 2-pinnate, obscurely or plainly spinulose-serrate. 



