620 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiii. 



The cost of Professor Eaton's volumes has been such, unfortunatelj^ 

 as to place them be^'ond the reach of a majority of fern students; and 

 largely on this account it has remained for Professor Underwood's 

 attractiye little book to really popularize the stud}" of ferns within the 

 United States. The tirst edition of the latter appeared in 1881, and 

 was entitled Our Natiye Ferns and How to Stud}' Them. It contained 

 116 pages, the lirst half being deyoted to chapters on the haunts, habits, 

 and distribution of ferns, their morphology and structure, methods of 

 study, and the like; the remaining portion comprising a systematic 

 arrangement of the groups treated by Eaton in his larger work. The 

 second edition, made necessary by a remarkable demand for the first, 

 appeared the following year under the slightly emended title. Our 

 Natiye Ferns and Their Allies, preserving the general scheme of the 

 former volume, but extending the systematic treatment to include the 

 Equisetaceae, Marsileaceae, Salviniaceae, Lycopodiaceae, Selaginella- 

 ceae, and Isoetaceae, which had merely been listed in the first edition. 

 The third edition appeared in 1888, being practically an enlargement of 

 the preceding. The fourth was issued in 1893, and contained a num- 

 bei- of nomenclatorial changes — notably the substitution of Dryopteris 

 for Aspidium — to bring the nomenclature to the standard set by the 

 "Rochester code." The lifth edition (1896), except for the addition 

 of a few species, is practically like the fourth. The sixth and last, 

 which appeared in June, 1900, is extensively remodeled in conformity 

 with the author's views as set forth in part in a Review of the Genera 

 of Ferns proposed prior to 1832.^ The most notable changes have to 

 do with matters of nomenclature, though the systematic arrangement 

 is also considerably modified and the number of species increased. It 

 is hardly to be supposed that further studies will not result in addi • 

 tional changes; nevertheless nothing is more certain than that the 

 present edition represents the most logical sequence of genera and the 

 most reasonable estimate of our species that has yet been presented. 

 Its general scheme has been followed closely in the preparation of the 

 present paper. 



Owing to the fact that Professor Underwood's is essentially a popu- 

 lar treatise, all citations are naturally and properly omitted. In the 

 Ferns of North America, on the other hand, we have extensive but 

 often incomplete bibliography under each species; but notwithstand- 

 ing its incompleteness there has hitherto appeared no index of syn- 

 onyms or compendium of any sort to take its place. The present list 

 has been prepared, therefore, with the object of atifording full citations 

 for all the included species and for the more important synonyms. 

 An especial ell'ort has been made to insure the accurate citation of 

 references to all original descriptions. It has been impossible to verify 

 without exception every citation; but the number unverified is very 



^ Mem. Torr. Club 6 : 247-283. 1899. 



