56 



EXPLANATIONS OF THE FORMULA. 



It is trusted that the preceding explanations will have 

 sufficed to render intelligible the sub-divisions of Britain 

 into provinces and climatic regions or zones, with the 

 grouping of plants into types of distribution. As before 

 mentioned, it appears more expedient to postpone full bo- 

 tanical descriptions of such sub-divisions and groupings, 

 until the distribution of the several species shall have been 

 first reduced into one common formula, adapted for easy 

 reference, and for corrective re-examination by the author 

 and other parties. But that formula itself may still require 

 some words of explanation, in the eyes of those persons 

 who are only commencing their studies in botanical geo- 

 graphy, and who are unacquainted with the former writings 

 by the same author. 



' The London Catalogue of British Plants,' published for 

 the Botanical Society of London, is adopted as a con- 

 venient index to the present work, until its completion. 

 The same names will be employed for the species, with 

 some few emendations, suggested by advancing knowledge ; 

 and the same numbers will also be retained with the names, 

 for the sake of uniformity in reference. The sign ' t \ af- 

 fixed to their names, will distinguish species which have 

 been ascertained to be British since publication of the 

 ' Catalogue.' Those which were excluded from the 'Cata- 



