154 BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 
the fact that the field. is almost entirely unworked, except from a 
purely descriptive standpoint. Luerssen has described the spor- 
angial groove in the genus Vittaria; Mettenius has figured a leaf 
section of a species of the same genus; E. C. Jeffrey, and E. G. 
Britton and A. Taylor have described and figured the leaf and 
stem structures of single species, also of Vittaria. Goebel has 
described the gametophytes of species in several of the genera and 
E. G. Britton and A. Taylor described the same stage in another 
species. There is, however, no occasion for considering these 
scattered papers except as of interest in connection with the 
detailed study. 
The present paper deals almost entirely with the comparative 
external morphology and venation of the genera and the probable 
relationships indicated by these characters. The data needed in 
this connection, as well as for the internal morphology on which it 
is intended to publish later, were obtained in the course of a taxo- 
nomic study of the species. The taxonomic problem is in many 
respects the most difficult of all, as the species are often very 
similar externally and require microscopic study, as in Jsoetes. 
The species groups will be revised from time to time as soon as 
sufficiently understood. Many of the necessary data for such 
revisions are now at hand. 
The material studied has been almost entirely in the form of 
dried herbarium specimens. Usually it has been possible to soak 
these and get fair sections when necessary, although in the case 
of poorly dried plants soaking does not produce the desired results. 
The work has been carried on during the last five years at the 
New York Botanical Garden, and mainly with the material in 
the Underwood Fern Herbarium at that place. Besides this 
material I have had also loans from the herbarium of the Botanisk 
Museum at Copenhagen, the Eaton Herbarium at Yale University, 
the National Herbarium at Washington, the herbarium of the 
Bureau of Science at Manila, and from Dr. E. B. Copeland’s private 
herbarium of Philippine ferns. I am grateful to those to whom I 
owe the privilege of examining the material in these herbaria, to 
Dr. N. L. Britton of the New York Botanical Garden, to Mr. Carl 
Christensen of the Botanisk Museum of Copenhagen, to Professor 
A. W. Evans of Yale University, to Mr. W. R. Maxon of the U. 
