116 POPULAR HISTOIIY OF LICHENS. 



the genera Licliina and Collema hold an anomalous position 

 in regard to the Algse, in which some botanists classify 

 them ; while Bmomyces and other genera occupy a similar de- 

 batable relation to the Fungi. Lichens may also be said to 

 be connected with the Mosses by the transition-group of the 

 Hepaticse, — of which the common Marchantia, or Liverwort, 

 a denizen of the damp, dark sides of rocks in the neighbour- 

 hood of streams or waterfalls, is a familiar example. 



After what we have said on the subject of the bases of 

 Classification, when describing the history of Lichenology 

 in our first Chapter, we need make no apology or justifica- 

 tion for preferring, in the following arrangement of British 

 species, a natural to an artificial classification — a classifi- 

 cation founded on natural affinities or structural analogies, 

 rather than one based on the vegetative or reproductive sys- 

 tem of Lichens exclusively. We cannot advance a com- 

 plete natural system of classification ; nor can this be done 

 until our knowledge of the natural history of the Lichens 

 is greatly improved and extended. "We consider the dis- 

 tinctive marks of Lichen-species to be at present very im- 

 perfect and unsatisfactory ; many genera and species stand 

 in a most anomalous position in regard to their alliances, 

 and the progress of Lichenology must soon result in a com- 

 plete revolution in the classification and nomenclature of 



