INTRODUCTION. 



Aside from their esthetic value, our native Pteridophytes 

 are of little practical use, and this may be said of most of the 

 species living in the world today. Ecologically considered, how- 

 ever, they are of considerable importance, and in the past geo- 

 logical ages also, the ferns and their allies were most important 

 plants, contributing largely to the formation of coal. 



It is hoped that this presentation of the Ohio species will 

 enable all who so desire to become acquainted with these most 

 graceful plant forms. 



The keys have been made very complete so that one should 

 be certain of the specimen in hand when the name has been 

 traced out, except perhaps in a few of the more difficult genera. 

 Only brief descriptions have been given in the catalog of species, 

 and usually the characters enumerated in the keys have not been 

 repeated. 



The list of Ohio Pteridophytes, as it now stands, contains 

 6 1 species and a number of varieties, all being represented by 

 herbarium specimens. Unless otherwise stated the records are 

 based on specimens in the state herbarium of the Ohio State 

 University. It is possible that several other species will be found 

 in the state. 



The census of species is as follows : 

 Ferns — 44 species. 

 Equisetums — 8 species. 

 Lycopods — 6 species. 

 Water-ferns — i species. . 

 Ouillworts — No species. 

 Selaginellas — 2 species. 



Among those who have published lists of the Ohio ferns 

 and fern allies, either separately or in some more extensive 



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