GENERA OP FERNS AND THEIR CLASSIFICATION. 63 



natural groups and sequences are obtained than by a 

 strict adherence to the artificial characters affcrded 

 by the fructification and venation. Among I'erns 

 no single organ alone affords characters sufficient for 

 general systematic purposes. Were the principle 

 upon which Linneeus acted — that is, a strict adherence 

 to the fructification alone — applied in its integrity 

 to the enormous mass of Ferns now known, — and it 

 would be quite possible to do so, the most incongruous 

 plants would be associated under one genus, and the 

 magnitude of the genera would be quite overwhelming. 

 The same would be the case were venation alone or 

 habit alone to be taken into consideration. In some 

 instances, however, a marked difference in one set of 

 characters indicates well-defined groups ; but as a 

 general rule a combination of differences in two or 

 more sets is requisite. Great difference of opinion 

 exists as to what is and what is not a genus ; but so 

 long as plants are distributed into well-circumscribed 

 groups of not too great an extent, it appears to mo 

 that it is a matter of little importance whether those 

 groups be termed genera, sub-genera, or sections. 

 For' my own part I prefer regarding them as genera. 



It has not been without due consideration that I have 

 arrived at this conclusion. It also saves a great deal 

 of unnecessary trouble, both in speaking and writing 

 about Ferns, it being more easy to say and write 

 Elajphoglossum conforme, than Acrostichum (Elapho- 

 glossum) conforme, or Gymnogramme tomentosa, than 

 Gymnogramme (Eiigymnogramme) tomentosa, &c. Also 

 by studying the character of the smaller groups indi- 

 vidually, and treating them as genera, their nature is 

 at once brought to the mind, without having to think 



