114 OUR NATIVE FERNS AND THEIR ALLIES. 



tanum Baker.) Unalaska, Mount Dawson, British Columbia 

 (Macoun), 



tt Lower pinna little smaller than those above. 



12. A. thelypteris Swz. (MARSH-FERN.) Rootstock slen- 

 der; fronds i 2 long, 4' 6' broad, lanceolate, pinnae mostly 

 horizontal, linear-lanceolate ; segments oblong, entire, obtuse 

 or appearing acute in fruit from the strongly revolute margins; 

 veins mostly forked, bearing the sori near their middle ; indusia 

 minute, smooth, and naked. (Polypodium thelypteris L., Ne- 

 phrodium thelypteris Desv. , Lastrea thelypteris J. Sm.) North- 

 ern United States to Florida. 



13. A. patens Swz. Rootstock rather stout, bearing several 

 fronds at the growing end ; fronds 2 3 long, 4' 10' broad, 

 ovate-oblong, softly pubescent beneath ; pinnae closely placed, 

 linear-acuminate, lowest pair somewhat deflexed, all cut three- 

 fourths of the way to the midrib ; segments numerous, acutish, 

 basal ones longest; veinlets evident, lowest ones of adjoining 

 segments often uniting; sori near the margin; indusia very 

 pubescent. (A. molle Kunze.) Florida to California. 



** Texture firmer or sub-coriaceous, veins forking freely. 

 t Fronds pinnate; pinnce cut into spreading triangular lobes; 

 sori confluent. 



14. A. unitum R. Br., var. glabrum Mett. Stipes i 1^ 

 long, brownish, naked; fronds i or more long, 5' 8' broad ; 

 pinnae narrow, cut from one third to half-way down into sharp, 

 pointed lobes; lower pinnae not reduced; veins pinnate in the 

 broad lobes with 6 8 veinlets on each side, the lower ones of 

 contiguous groups united ; sori near the ends of the veins prin- 

 cipally in the lobes. Florida. 



ft Fronds bipinnatifid or bipinnate ; indusia rather large ; 

 segments not spinulose. 



\ Fronds small, narrowly lanceolate. 



15. A. fragrans Swz. Fronds 4' 12' high, glandular and 

 aromatic ; pinnae linear-oblong, pinnately parted ; segments 

 toothed or nearly entire, nearly covered beneath with the very 

 large thin imbricate indusia, which are orbicular with a narrow 

 sinus, the margin ragged and sparingly glanduliferous. (Ne- 



