Key to the Genera 
Leaves ample. 
Terrestrial plants. 
Leaves divided into one fertile and one sterile 
segment. 
Segments undivided, plants 1-3 dm. high ; 
sporophyll a distichous spike. 
1 . OpH[0 3LOSSUM. 
Segments dividsd, spDrophyil pinniite -3- 
pinnate. 2. Boti?ychium. 
Leaves bearing sporecases upon branched pin- 
nae w^ithout parenchyma. 
Plants trailing ; leaf-segments 4-7 palm.iti- 
fid. 3. Lygodium. 
Plants robust, erect, 6-20 dai. high. 
4. OsVUTNDA. 
Sporecases forming sori on the lower side of the 
leaf. 
Sori without indusia ; roolstocks creeping. 
Leaves pinnatifid. 
a. glabrous. 5. Polypodium. 
b. scaly. 6. Marginaria. 
Leaves triangular, 2-pinnatifid. 
7. Phegopteris. 
Sori borne upon a revolute portion of the leaf 
margin ; stipes straw^- or dark-colored.' 
Leaves ternate, branches 2-pinnate. 
8. Pteridium. 
Leaves pinnate, 2- pinnate below. 
9. Pell^a. 
Leaves 2-3pinnate, pinnules pinnatifid. 
10. Cheilanthes. 
Leaves decompound, pinnules triangular 
oblong. IL Adtantum. 
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