4 POLYPODIACEAE 



5. DRYOPTERIS Adans. 



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

 orbicular indusium fixed by the sinus. 



1. D. Thelypteris (L.) A. Gray. BOG FERN. Eootstooks slender, 

 long, creeping, black : stipe smooth, 9 / -20 / high : frond 9 / -12 / long, 

 pinnate and slightly downy : pinnae 1/-2' long, long-lanceolate in out- 

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

 veinlets forking : indusium reniforni. 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 FERN. 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. ) Roth. LADY FERN. Fronds numerous, 

 from a rather stout rootstock, 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. parvulum. 



Sori numerous, crowded. 3. A. platyneuron. 



1. A. angustifolium Michx. TALL SPLEENWORT. 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 SPLEENWORT. 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 bluffs near Courtney. 

 The station has since been destroyed. June-October. 



