114 OUR NATIVE FERNS AND THEIR ALLIES. 



tanum Baker.) Unaiaska, Mount Dawson, British Columbia 

 (Macouri). 



ft Lower pinnce little smaller than those above. 



12. D. thelypteris (L.) Gray. (MARSH-FERN.) Rootstock 

 slender; 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 mid- 

 dle; indusia minute, smooth, and naked. (Polypodium thelyp- 

 teris L., Nephrodium thelypteris Desv., Lastrca thelypteris J. 

 Srn.) Northern United States to Florida. 



13. D. patens (Swz.) Ktze. Rootstock stout, bearing sev- 

 eral 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 ad- 

 joining 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 ; pinna cut^into spreading triangular lobes ; 

 sori confluent. 



14. D. unita (L.) Ktze., var. glabra (Mett.) Unde. Stipes 

 i 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. D. fragrans (L.) Schott. Fronds 4' 12' high, glandu- 

 lar-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 

 ginus, the margin ragged and sparingly glanduliferous, (JS T e,- 



