PREFATORY NOTE. 



The rearrangement of the British lichens in the Herbarium of the 

 British Museum and the incorporation of a great series of specimens 

 made a revised Catalogue of these plants a necessity. 



The large number of authentic specimens from Dillenius, Hudson, 

 Sowerby, Dawson Turner, T, Taylor, Salwey, Mudd, and Leighton 

 contained in the Herbarium supplied material for determining the 

 species of these lichenologists which does not exist elsewhere : while 

 the extensive series of British Lichens, including the collections of 

 Buddie, E. Forster, R. Brown, Carroll, Piggot, Holl, Crombie, and 

 Larbalestier, made it possible to determine with certainty the 

 geographical distribution of the species within the British Islands. 



The E.ev. J. M. Crombie, M.A., undertook the preparation of a 

 Monograph based on these materials. This volume contains descrip- 

 tions of half the known British species. The remainder (consisting 

 of the Lecideei, Graphidei, Pyrenocarpei, Peridiei, and Myriangiacei) 

 is so advanced that it may be expected to appear in ]8!!5, and 

 will contain a complete index to the genera and species of the 

 ^\hole work. 



WILLIAM CAIIRUTHER8. 



March 18'J4. 



