2 POLYPODIACEAE 



2. B. obliquum Muhl. Orapb Fben. 8'-12' high : roots very 

 fleshy : sterile portion of frond long-stalked from near base of plant, ter- 

 nate : primary segments once or twice pinnatifid : ultimate segments 

 stalked, obliquely lanceolate. — Five plants in rich woods along the base 

 of the Missouri River bluffs in two stations near Sibley. Fall. 



Family 2. OSMUNDACEAE R. Br. 



Differs from Polypodiacbae in the sporangia having no elastic ring 

 or very slight traces of one. Sterile and fertile portions of frond very 

 dissimilar. Fertile pinnae much contracted, bearing the sporangia on 

 the margins of the narrow segments. 



1. OSMUNDA L. 



Tall ferns growing in large clumps from thick rootstocks. 



1. O. Claytoniana L. Flowering Fern. Fronds 2°-4° high, fer- 

 tile in the middle ; fertile pinnae 2-5 pairs, brownish at maturity, soon 

 withering away : sterile pinnae lanceolate in outline, deeply cleft into 

 oblong segments. — Occurs sparingly in moist sandy woods in the vicinity 

 of Sibley. May-June. 



Family 3. POLYPODIACEAE R. Br. 



Sporangia having an elastic ring which splits open and discharges the 

 spores. Sporangia borne in clusters (sori) on the back or margins of the 

 frond. Rootstocks usually slender and horizontal. Sori covered by an 

 ^ndusium, or naked. 



Sterile and fertile fronds very dissimilar. 

 Sterile and fertile fronds similar. 

 Indusium formed of margin of frond. 



Indusium continuous around each segment. 

 Indusium not continuous around each segment. 

 Indusium not formed from the frond margin. 

 Fronds white and powdery on lower surface. 

 Fronds not white and powdery on lower sur- 

 face. 

 Sori linear in outline. 



Fronds entire, rooting at apex. 

 Fronds pinnate. 

 Sori straight. 

 Sori curved. 

 Sori round or roundish. 

 Fronds evergreen. 

 Bog herbs. 



Fronds not evergreen and plants not grow- 

 ing in bogs. 

 Stipes chaffy ; fronds grandular-puberu- 2. WooDslA. 



lent. 

 Stipes almost smooth : fronds smooth. 3. Filix. 



