xiv PREFACE. 



Much valuable assistance in the preparation of this 

 book has been given me by students of the fern allies. 

 The source of many notes has'been indicated in the text, 

 but I am especially indebted to, and wish here to thank, 

 Mr. S. B. Parish, Mr. A. J. Hill, Mr. C. H. Demetrio, 

 Dr. C. B. Graves, Mr. J. B. Flett, Mr. Julian Reverchon, 

 Prof. R. S. Cocks, Mr. Thomas Howell, Mr. M. L. 

 Fernald, Mr. J. H. Ferriss, Miss E. Cannon, and Miss L. 

 F. Kimball. Mr. Alvah A. Eaton, of the Ames Botani- 

 cal Laboratory, whose studies of these plants have con- 

 tributed so much to our knowledge, has rendered 

 invaluable assistance by the loan of specimens, by send- 

 ing many interesting notes, and by a critical reading of 

 the proof. It is but fair to add, however, that in matters 

 of nomenclature and the limitations of species I have 

 not always followed his suggestions. 



WILLARD N. CLUTE. 

 Joliet, 111., 



February 27, 1905. 



