GENERA OF FERNS AND THEIR CLASSIFICATION. 67 
which is very well represented in “ Lowe’s Ferns/ 5 
vol. v. p. 47. 
These observations briefly explain a few of the causes 
of the plurality of names possessed by most Ferns, 
also the difficulty of arriving at satisfactory conclusions 
respecting their generic and specific distinctions, 
affording little hope of an early unanimity amongst 
authors, and fully justifying every one who has studied 
Pteridology in giving his own views. 
This being the case, I have to explain that some 
important changes in the relative position of tribes 
and genera have been made in the following enumera- 
tion, in order to bring natural allied genera together ; 
thus Oleandra and the articulated Davallia are now 
placed in Epemobrya, which is their proper place. 
The tribe Aspidiece I now make a section of the tribe 
Phegopteridece, then* former separation being entirely 
dependent on the presence or absence of indusia, an 
organ not to be depended on in this tribe, when in 
many cases I am doubtful even of its value as a generic 
i distinction, such as between Didyopteris and Aspidium, 
, Goniopteris and Nephrodium, Phegopteris and Lastrea, 
these genera containing species perfectly analogous to 
I one another in general habit. The fugaceous nature 
of the indusium also makes it an organ of less import- 
ance than it is generally considered. In many species 
it is very small, and is soon lost or obliterated by the 
swelling of the sporangia; it is therefore only by 
watching living plants while the sori are yet young, 
that many species can be proved to be indusiate or 
non-indusiate. 
I have long been dissatisfied with the position of 
H ymenophylleoe as a section of the tribe Dicksonieoe , it 
f 2 
