CLASSIFICATION. 117 



British Lichens. Under these circumstances we think it 

 preferable only to describe the characters of typical and 

 familiar species, believing that an enumeration even of the 

 mere names of rare species and puzzling varieties would 

 serve only to confound and alarm the beginner, for whom 

 this little work is chiefly intended. 



In our arrangement and description of most of the Gym-*, 

 nocarpous Lichens, or those in which the thalamium is typi- 

 cally open, we have followed Schserer's e Enumeratio critica 

 Lichenum Europseorum' (Berne, 1850) ; and in those of the 

 Angiocarpi, or Lichens in which the thalamium is typically 

 closed, as well as of the Gymnocarpous Natural Order Gra- 

 phiclea, Leighton's c British Species of Angiocarpous Lichens 

 elucidated by their Sporidia' (Ray Society, London, 1851) 

 and his c Monograph on the British Graphideae' (Annals of 

 Natural History, London, 1854). On these valuable con- 

 tributions to Lichenology the descriptive part of this Work 

 is mainly founded ; to their pages we must refer all desirous 

 of prosecuting the subject beyond its mere skeleton or out- 

 lines."^ We are also under deep obligations to the memoir 



* To this statement it may be advisable to add the following qualification, — 

 that we do not regard the classification in these works as at all approaching 

 perfection ; there are many points on which we differ materially from their 

 authors. They are however the most recent works on their respective sub- 

 jects, and contain comparatively the greatest amount of correct information. 



