30 
IOWA ACADEMY OP SCIENCE 
CYSTOPTERIS Bernh. 
14. Cystopteris bulbifera (L.) Bernh. Bulbiferous Bladder Fern. 
Yery plenty on limestone exposures. 
15. Cystopteris fragilis (L.) Bernh. Common Bladder Fern. Com- 
mon in woodlands. 
WOODSIA R. Br. 
16. Woodsia obtusa (Spreng) Torr. The Obtuse Woodsia. Common 
in densely wooded places. 
ONOCLEA L. 
17. Onoclea sensibilis L. Sensitive Fern. Yery plenty in woodlands. 
18. Onoclea struthiopteris (L.) Hoffim. Ostrich Fern. Not rare in 
moist woodlands. 
OSMUND IACEAE . 
OSMUND A (Tourn) L. 
19. Osmunda claytoniana L. Interrupted Fern. Yery plenty in 
woodlands. 
OPHIOGrLOSSACEAE. 
BOTRYCHIUM Sw. 
20. Botrychium virginianum (L.) Sw. Rattlesnake Fern. Not rare 
in woodlands. 
EQUISETACEAE. 
EQUISETUM (Tourn) L. 
21. Equisetum arvense L. Common Horsetail. Common in sandy 
soil. 
22. Equisetum sylvaticum L. Woodland Horsetail. Not rare in damp 
and shaded spots. 
23. Equisetum robustum (A. Br.) A. A. Eaton. Stout Scouring Rush. 
Plenty in gravels. 
24. Equisetum laevigatum A. Br. Smooth Horsetail. In fields and 
roadsides. 
