PREFACE. xiii 



thirteenth volume, which enjoys the unique distinction 

 of being the only publication in the world devoted to 

 the ferns and fern allies. In past volumes it has 

 publislied much regarding the haunts and habits of the 

 plants, including descriptions of many new species and 

 forms. A series of Fern Floras of the States is now 

 being published, which gives lists of the ferns and fern 

 allies in each State, with distribution and other notes 

 added. 



In the matter of nomenclature I have adopted a some- 

 what conservative treatment, preferring for the most part 

 the names commonly used, since these will be most fre- 

 quently found in other books. When they differ from 

 others recently proposed, the latter are given also, and 

 they have also been included in the Checklist of the 

 species. It does not seem advisable, in a work of this 

 kind, to follow the practice of radical botanists in treat- 

 ing a large number of forms as species. It is possible 

 that some of these forms may be found to have characters 

 of specific importance, but it will be less confusing to 

 the beginner if they are still regarded as forms of the 

 species from which they have been segregated. 



These newly named forms have had to be recognized, 

 however, and in giving them what I believe to be their 

 rightful places a number of new combinations have un- 

 avoidably been made. In no other way has it seemed 

 possible to indicate to beginners the various disguises 

 under which certain plants are likely to be found in com- 

 ing years. In the Checklist I have followed the plan 

 of citing the authority for the species only, believing 

 that the author of a new combination is not entitled to 

 the prominence which a double citation of authorities 

 confers. 



