The Rovtance of a Wayside Weed. 6 1 



Scotland are plants which once spread uninterruptedly 

 from Yorkshire to Scandinavia, during the same 

 period ; while both classes have been afterwards 

 isolated in Britain by the gradual subsidence of the 

 intervening land. But this still leaves unanswered the 

 question, Whence did we get the Pyrenean types ? 



Perhaps one might be disposed at first sight to 

 fancy that they came over separately, as we know a 

 few American plants have really done. There is the 

 well-known Canadian canal weed, which was intro- 

 duced by a botanist into a tank near Cambridge in 

 1845, and rapidly spread over all England ; there are 

 a few orchids and other wild flowers whose seeds have 

 apparently been carried across the Atlantic on the 

 feet of birds ; and there are some half-dozen escaped 

 garden flowers, like the evening primrose, which have 

 established themselves easily among some rare warm 

 spots in our congenial climate. Possibly it might 

 seem as though the arbutus, the hairy spurge, the 

 Mediterranean heath, and all the rest of the southern 

 species in South-Western England or Ireland had got 

 across to us in somewhat the sime fragmentary 

 fashion, and had succeeded in effecting a foothold 

 only in these warmer Cornish and Irish nooks. But 

 there arc a great many reasons against believing this. 

 In the first place, we have the immense number to 



