GENEEA OF TEENS AND THEIE CLASSIFICATION. 67 



which, is very well represented in " Lowe's Ferns/' 

 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 Eremobrya, which is their proper place. 

 The tribe Aspidiece I now make a section of the tribe 

 fkegopterideoBy their 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 

 distinction, such as between Dictyopteris and Aspidium, 

 Goniopteris and Nephrodium, Pliegopteris and Lastrea, 

 these genera containing species perfectly analogous to 

 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 

 HymenophyllecG as a section of the tribe Dickso?iiece, it 



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