Key to the Genera. 
Leaves ample. 
Terrestrial plants. 
Leaves divided into one fertile and one sterile seg- 
ment. 
Segments undivided, plants 1--3 dm. high; 
sporophyll a distichous spike. 
I, Ophioglossum. 
Segments divided, sporophyll pinnate to 3- 
pinnate. 2. Botrychium. 
Leaves bearing sporecases upon branched pin- 
nae without parenchyma. 
Plants pretling leaf-segments 4--7-palmati- 
fid. 3. Lygodium. 
Plants robust, erect, 6--20 dm, high. 
4. Osmunda. 
Sporecases forming sori on the lower side of the 
leaf. 
Sori without indusia ; rootstocks creeping. 
Leaves pinnatifid. 
a. glabrous 5. Polypodium. 
b. scaly. 6. Marginaria. 
Leaves triangular, 2--pinnatifid. 
7. Phegopteris. 
Sori borne upon a revolute portion of t he 
leaf-margin ; stipes straw- or dark-col- 
ored. : 7 | DSI : 
