PREFACE. \ II 



Further changes consist in the withdrawal of the bibliography follow- 

 ing each species name, the arrangement of the synonymy in chrono 

 logical order, and the insertion of the dates of publication. The 

 names of periodicals have also been substituted in the citations foi 

 subtitles, and a number of names which are clearly nomina inula have 

 been withdrawn. One new specific name has been changed because it 

 was found to be a homonym. 



Tin 4 seventh and last paper is ••Studies of Tropical American 

 Finn- No. L," by William R. Maxon. During the last decade the 

 National Museum has acquired large collections of Mexican and Cen- 

 tral American plants. These collections are rich in new material, but 

 evidently they are not sufficiently comprehensive to warrant undertak- 

 ing the publication of a general flora of anyone of these countries 

 without further exploration. In order, however, to make public the 

 scientific results of preliminary studies of the collections a series of 

 papers has been carried on in the Contributions from the National 

 Herbarium, under the title " Studies of Mexican and Central Ameri- 

 can Plants," by Dr. J. N. Rose, Associate Curator. It i^ now proposed 

 to begin a similar series under the title tfc Studiesof Tropical American 

 Ferns," by Mr. William R. Maxon, Assistant Curator. Although at 

 present this will deal largely with Mexican and Central American col- 

 lections, it will include also descriptions of new and noteworthy West 

 Indian species. South American forms will be considered also, as cir- 

 cumstances may require. 



Frederick V. Coville, 

 Curator of tlu I nited States X<if<<>/nil Herbarium. 



