214 NATURAL HISTORY. 



It is to be remembered, to begin with, that in dealing 

 with this problem, Forbes started with a firm belief in the 

 doctrine of ' specific centres/ or geographical points from 

 which the individuals of each species have slowly diffused 

 themselves. The problem before Forbes, therefore, was 

 how to account, on the basis of ' specific centres,' for the 

 present distribution of animals and plants in Britain. As 

 regards the plants, which alone we shall consider here, 

 Forbes showed that there exist in Britain certain well- 

 marked areas or regions, characterised by peculiar types 

 which do not occur elsewhere. Of these botanical pro- 

 vinces he distinguished five, as follows : 



(I.) An area which may be spoken of as the ' Asturian 

 area,' comprising the mountainous districts of the west and 

 south-west of Ireland. Here we meet with a number of 

 peculiar plants, comprising the Arbutus, the Mediterranean 

 Heath (Erica mediterranea\ and several peculiar species of 

 saxifrages. The nearest point in Europe where the same 

 plants are found growing as natives is in the Asturias, in 

 the north of Spain. 



(II.) A second area comprises the south-west of England 

 (Devonshire and Cornwall principally), together with the 

 south-east of Ireland. In this area we find a number 

 of plants of what may be called the 'Armorican' type, 

 unlike those found in Britain generally, but intimately 

 related to the plants of the Channel Islands and of 

 Brittany and Normandy. Amongst these are the Cornish 

 Heath (Erica vagans), the Wild Madder (Rubiaper^rina\ 

 the French Tamarisk (Tamarix gaUica), and various other 

 peculiar forms. 



(III.) A third area comprises the south-east of England, 



