PLANT DISTRIBUTION AND ASSOCIATIONS. XX111. 



is composed of weeds, like the dandelion and chickweed, which 

 have followed in the track of civilisation ; but if the review is 

 limited to temperate regions, a considerable number of aquatic 

 plants should also be added, for these are, undoubtedly, the 

 most cosmopolitan in their nature, owing to their environment 

 being the least affected by climate. On comparing the flowering 

 plants of Halifax with those of Minnesota, U.S.A., not more 

 than sixty or seventy are common to the two floras, and of 

 these more than half are aquatic plants, or hydrophytes, a pro- 

 portion which is greatly in excess of their relative numbers in 

 either flora. 



(2.) Germanic, or Asiatic species. The general British 

 Flora, embracing a majority of the whole, ranges more or less 

 over Europe and Asia, and to a less extent northern Africa. 

 Such plants have arrived here at different times, and by differ- 

 ent routes, from the east, but this western migration originated 

 not in Germany, as the older name seems to imply, but in 

 western Asia. The following cases will illustrate the varied 

 regions now occupied by members of this family, of which the 

 cosmopolitan species are also really members, with an excep- 

 tionally wide distribution. The Lesser Celandine is found 

 throughout Europe and western x\sia ; Ivy in western and 

 southern Europe, northern Africa, western Asia and Japan ; 

 Primrose in south and central Europe and northern Africa, 

 but is absent in north-eastern Europe and Siberia ; Heather 

 (Galium) in northern and central Europe, western Siberia, 

 Azores, Greenland, and very rarely in north-eastern America. 



(3.) Western and Atlantic species, Our two heaths, 

 however, have a much more restricted range than the heather, 

 and whatever their past history has been, they are now limited 

 to western Europe, attaining their maximum development 

 along the Atlantic coast. Other British heaths are found only 

 in the south-west of England and in Ireland, and in the south- 

 west of Europe. Though these are not present in this district, 

 a few members of this very remarkable group are* notably the 

 filmy fern (now in all probability extinct) ; the ivy-leaved hair 

 bell (Wahlenbergia) ; the blue-bell, the earthnut, and the 

 autumn Crocus, though its origin in England is problematical. 

 Some of these certainly belong to a type which has reached 

 the British Isles from the south, viz. the Iberian peninsula ; 

 and they exhibit such a preference for the Atlantic border, 

 that they are much more strongly developed in Ireland, and do 

 not occur in the east of England at all. 



