ON GENERA AND SPECIES. 73 



" the finest in cultivation," it in 1864 consisted of nearly 

 one-half of the number of the species described by him in 

 that work, but of these the learned author made less use 

 than might have been expected. This was consequent on 

 findings a considerable difference in describing; species from 

 living' plants and herbarium specimens ; for in many cases 

 it was found that it was not till specimens of the cultivated 

 plants were dried that they could bo identified with native 

 specimens of the same supposed species in the herbarium ; 

 consequently the descriptions in the " Species Filicum " 

 are, with few exceptions, entirely founded on specimens in 

 the author's herbarium. 



With me it was otherwise : the living collection re- 

 quiring daily care and attention, led me to become 

 acquainted with the special habits and modes of growth of 

 the different species ; and this has enabled me draw up the 

 following natural arrangement. I say natural, but it must 

 be understood that any sequence of allied genera has its 

 limit, and that it is only in individual tribes that genera, 

 in most cases, can be so arranged as to form natural 

 transitions from one to another. By this several tribes 

 become naturally connected, while others, such as Aspleniecp, 

 Hymenophylle'X, and Gleiclieniea, may be called independent 

 tribes. 



The principle of the following arrangement is based on 

 the different modes of vernation and habit. It begins 

 with the division Eremobrya, followed by Desmobrya and 

 Soaphobrya ; each of these divisions are divided into tribes, 

 of which there are twenty-nine in all ; each tribe contains 

 a greater or lesser number of genera, and the genera of 

 each tribe when possessing any well marked difTerential 

 characters are arranged under sections. The characters of 

 each genus are given, beginning with the nature of the 



