6 PREFACE. 
field. Our knowledge of spores and sporelings is far 
from complete; the prothallia of some species have 
never been seen; the phenomena of fern hybridization 
have scarcely been touched upon; while the study of 
the natural variation in species will afford much profita- 
ble work. There is also the ever delightful occupation 
of exploring unfamiliar territory and the possibility of 
thus adding to our knowledge of the distribution of 
species. The range of each species has been given in 
accordance with our present information, but it is ex- 
pected that many will prove to be more widely dispersed 
and that some now marked rare will ultimately be found 
to be more abundant. I shall be pleased to receive 
further information upon these points and will also 
undertake to identify any ferns that may be sent me 
provided that good fruiting specimens with rootstock, 
when possible, be selected for the purpose. 
In the preparation of this volume, I have had the 
hearty codperation of American fern students and take 
this opportunity to express my indebtedness to them. 
My thanks are especially due to Mr. William R. Maxon 
for data regarding the range of many species, to Mr. 
George E. Davenport for verifying the nomenclature 
of the Check-List, to Mr. B. D. Gilbert for carefully 
reading the proof-sheets, and to Prof. L. M. Underwood 
for much valued information. 
WILLARD N. CLUTE. 
Binghamton, N. Y. 
April 12, 1go1. 
