CHARACTEES OF TEIBES AND GENERA. 85 



terminal, lateral or compital, punctiform, oblong, or by 

 confluence linear naked. 



OBS. This tribe consists of about 200 described species. 

 The greater number come under the genus Polypodium, as 

 characterised by early authors, that is in having puncti- 

 form naked sori. The greater mass of the species have 

 anastomose venation, from simply reticulated to compound, 

 with free veinlets terminating in the areoles. In many 

 cases this difference alone is not sufficient to define natural 

 genera ; to do so it is necessary to make habit and any other 

 special structure of the fronds an important character in 

 arranging the species into natural groups, which, on 

 account of the gradual transition, it in many cases becomes 

 difficult to determine the group in which the transition 

 species should be placed. Authors are much divided on 

 this point, for instance, the venation of Phymatodes as 

 characterised by Presl, I in 1841, considered it did not 

 differ from the earlier founded genus Drynaria of Bory, 

 while Moore, in his " Index Filicum," places the whole of 

 Presl's Phymatodes, with the exception of the section Dry- 

 naria, under the early named genus Pleopeltis, also in- 

 cluding under it the whole or a portion of the species of no 

 less than twenty-four genera of different authors. Of 

 Drynaria of Bory he says, "We have kept separate the 

 very distinct-looking little groups of Drynaria and Dipteris, 

 the former distinguished by its peculiar sessile, sterile 

 fronds, the latter by its peculiar dichotomo-palmatafid 

 fronds, rather perhaps than by differences of higher value." 

 After having carefully considered the different views of 

 authors, and having had examples before me of the greater 

 number of known species, I have been led to arrange the 

 tribe Polypodece as follows : 



