PREFACE. 
The accompanying paper, by Mr. William R. Maxon, aid in crypto- 
gamic botany, United States National Herbarium, is a fragmentary 
contribution to our knowledge of the fern flora of the southern coun- 
tries of North America. The conclusions reached by the author are 
the result of a careful study of a limited series of specimens. They 
serve to suggest how large an amount of new systematic facts are 
likely to be discovered by an exhaustive collection and thorough her- 
barium study, by modern taxonomic methods, of the fern flora of 
tropical America. 
FREDERICK V. COVILLE, 
Curator of Botany. 
- III 
