The Origin of our British Flora 



sidered as consisting mainly of the four great invading 

 armies of plants. 



In the North, in some parts of West Ireland, and upon 

 the Scotch, Welsh, and a few English mountains, we still 

 find Dryas and its little willows, and other characteristic 

 arctic or alpine plants. 



The birch association is but seldom represented, but 

 shrubs of birch, rowan, larger willows and junipers, occur 

 on steep corrie sides and other places where they cannot 

 be destroyed by sheep. 



Lower down most of the heather moorland, diversified 

 by the silvery sheen of the cotton-grass, peaty mosses, or 

 rushy grass pastures, represent the old Scotch pine forests. 



In the fertile, low-lying parts of Scotland, oak forest 

 used to cover most of the country, but it is now 

 replaced by arable land or permanent pasture. The 

 valley floors or flat river holms seem, as we have shown 

 elsewhere, to be due to the reeds (Phragmites and others), 

 which choked unnecessary water channels and inter- 

 cepted the river silt. 



Besides these main groups, which form a very large 

 proportion of the Scotch flora, there are several other 

 and distinct divisions. The number of weeds is very 

 great but can never be accurately estimated, for with 

 changes of cultivation some die out and strangers enter 

 in. All over Britain one finds the Canadian weed 

 Elodea, which seems to have first been noticed about 

 1843. The Chilian Mimulus has got a firm footing by 

 the southern Scottish rivers and burns, and occurs 

 abundantly even in the marshes of the Tay. Claytonia 

 siberica is establishing itself in the West of Scotland, and 

 seems to be extending its range annually. 



Many other interesting cases will be found in almost 

 any county flora, or in the pages of the Journal of 

 Botany^ and which show that the flora of Britain is 



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