18 Origin of the British Flora. 
siderable number of plants which are confined to the 
Eastern Counties, they, or at any rate the majority of 
them, have not a correspondingly eastern distribution on 
the Continent, and so many of them occur throughout the 
greater part of Europe, that the present local distribution 
in Britain may be, after all, climatic rather than geo- 
graphical. The Eastern Counties are considerably drier 
and more sunny than the others, in this agreeing more 
nearly with the mainland of the Continent. 
Our western plants, on the other hand, are very 
peculiar, for we find in Cornwall and Devon, and also in 
the West of Ireland, groups of plants characteristic of the 
Pyrenean region. These plants occur usually not as 
rarities but in profusion, so that in parts of the West 
of Ireland the common species which carpet the hill-sides 
are Iberian forms unknown elsewhere in Britain. There 
is also another peculiarity which must be taken into 
account when we discuss the origin of these outliers— 
though Pyrenean plants occur both in the south-west of 
England and in the West of Ireland, the species found in 
the two districts are not the same. Thus Cornwall pos- 
sesses two of the Pyrenean heath-plants, Evica ciliaris 
(another outlier of which occurs in Dorset) and Erica 
vagans; while the four found in the West of Ireland, 
Erica Mackayi, Erica mediterranea, Dabeocia poltfolia, 
and Arbutus Unedo, are all different from the Cornish 
ones. The only western plants common to the two 
regions are three spurges, two of which are sea-coast 
species. Nearly all the Pyrenean plants found in the 
British Islands, including the only tree belonging to this 
group, have minute seeds, the numerous large-seeded trees 
and plants which are associated with them in Spain not 
extending into Britain. 
Three American plants also occur in Ireland, but the 
