Ill 



TEMPERATE FLORAS 



25 



Numerical Distribution of Plants in Britain 



We will now give a few numerical statements as to the 

 comparative abundance of the species of plants in large and 

 small areas in various parts of the world, such facts having 

 a special application to the theory of evolution. The 5 5 

 counties of England and Wales (counting the three Ridings 

 of Yorkshire as counties) have usually areas from 500 to 

 2500 square miles ; and a considerable number of them 

 have had their plants enumerated in special catalogues or 

 floras. The following are the approximate numbers of the 

 flowering plants in a few of these : — 



Statistics of County Floras 



This table of the distribution of plants in our counties 

 is very instructive, because it shows us the influence of 

 diversity of soils on the number of species that can grow 

 and maintain themselves naturally as wild plants. This is 

 largely dependent on the extreme diversity of the geology 

 of our island, almost every geological formation from the 

 oldest to the most recent being represented in it. This 

 variety of soil seems to be much more important than 

 diversity of surface due to altitude, so that our lowland 



