4 POLYPODIACEAE 



5. DRYOPTBRIS Adans. 



Differs from the last genus chiefly in having the oordate-reniform or 

 orbicular indnsinm fixed by the sinus. 



1. D. Thelypteris (L.) A. Gray. Bog Fern. Eootstooks slender, 

 long, creeping, black : stipe smooth, O'-SO' high : frond Q^-IS' long, 

 pinnate and slightly downy : pinnae l'-2' long, long-lanceolate in out- 

 line, pinnatifid into oblong lobes, each pinna bearing from 10-18 sori : 

 yeinlets forking : indusium reniform. — In a bog along the foot of the 

 bluffs about two miles west of Sibley. July-August. 



6. CAMPTOSORUS Link. 



Low spreading ferns with undulate-margined fronds and linear sori 

 which are irregularly scattered on either side of the reticulated veinlets. 

 Indusium fixed lengthwise to the veinlet. 



1. C. rhizophyllus (L.) Link. Walking Fkbn. Fronds ever- 

 green, thick, cordate at base, gradually narrowing into a long, slender 

 tip, which takes root and forms a new plant : sori numerous. — In dense 

 patches on moss-covered rocks in shady woods throughout, but nowhere 

 common. June-October. 



7. ATHYRIUM Roth. 



Fronds twice pinnate with oblong or linear sori oblique to the midvein. 

 Indusia curved, fixed lengthwise to inner side of vein. 



1. A. Filix-foemina (L. ) Eoth. Lady Fern. Fronds numerous, 

 from a rather stout rootstook, 8'-30' long, oblong-lanceolate with about 

 twenty pairs of long-lanceolate pinnae : pinnae once pinnatifid, the seg- 

 ments incised. — A handsome symmetrical fern, locally common in sandy 

 woods west of Sibley. June-August. 



8. ASPLENIUM L. 



Fronds once pinnate. Sori linear or oblong, oblique to the midvein. 

 Indusia straight, fixed lengthwise to inner side of vein. 



Pinnae entire : l°-4° high. 1. A. angustifoUum. 

 Pinnae variously incised : low ferns. 



Sori few, not crowded. 2. A. parmlum. 



Sori numerous, crowded. 3. a. platyneuron. 



1. A. angustifoUum Michx. Tall Spleen wort. 2°-4° high : 

 pinnae 20-40 pairs, long-lanceolate, acuminate : sori crowded, covering 

 the lower surface of the pinnae. — Frequent in rich woods along the Mis- 

 souri River bluffs, especially west of Sibley. August-September. 



2. A. parvulum Mart. & Gal. Small Splebnwort. Stipes tufted, 

 black, short : fronds oblong-linear, 4'-12' long : pinnae 3"-5" long, 

 oblong, crenulate, auricled on the upper side : fruit dots one to seven 



pairs on each pinna, midway between the midvein and the margin. A 



few plants were found in 1884 in a thicket on the blufis near Courtney. 

 The station has since been destroyed. June-October. 



