XX INTRODUCTION. 



As to the choice of nomenclature I have been guided by very- 

 similar considerations to those which prompted the selection of 

 the above classification. The principle of priority in nomenclature 

 may be considered as universally accepted ; but the acceptance of 

 the principle is far from having produced, at present, that 

 uniformity which is one of the most important objects it sets out 

 to attain ; nor can uniformity be hoped for until there is a general 

 acceptance, not only of the principle of priority, but of the rules 

 by which the principle is to be carried out; the limits, for 

 example, of its retrospective action. Following out the principle 

 in question, Lindberg has arrived at a system of nomenclature 

 very widely differing from that of most works on bryology, and he 

 has been followed very closely by Braithwaite in the British Moss 

 Flora. I have not felt it desirable to conform to this nomenclature 

 however ; partly on the grounds above given, that it would tend to 

 confuse beginners who might be expected to have in their hands 

 chiefly such works as the London Catalogue of British Mosses, 

 Hobkirk's Synopsis, etc. ; partly because of the extreme doubtful- 

 ness as to the finality of the nomenclature in question ; and this 

 even apart from the question of the general acceptance of those 

 particular rules upon which the principle of priority has been 

 carried out by Lindberg. For it is seen that these rules them- 

 selves involve the almost indefinite impossibility of finality, since 

 there is always the chance of an earlier name being discovered 

 for a given species than the one whose priority is (for the time) 

 established ; a possibility exemplified at the present time in the 

 literature of the Sphagnacese in a very striking manner. 



I have therefore maintained the nomenclature employed by 

 Schimper (Synopsis, Ed. II.) as far as is compatible with the 

 somewhat different classification here adopted, except in the 

 following cases. When a name is pre-occupied for a phanero- 

 gamic or other class of plant (as in the case of Thamnium and 

 Homalothecium) I have, of course, dropped it and employed the 

 earliest alternative name. And in a few cases where Lindberg's 

 nomenclature has been used also in standard works of modern or 

 comparatively modern date (as in the case of Catharinea Ehrh. 

 = Atrichum P. Beauv.) I have taken it as an indication of a general 

 acceptance of the name and have employed it here. I hope that 

 these few changes, while insufficient to cause any great difficulty 

 to the student, may in a measure bridge over the difference 

 between the "old" and the "new" nomenclatures, and prepare 

 the way for the latter, without introducing any unaccustomed 

 names but such as it may be anticipated will be finally adopted. 



