The Present Flora of Britain. i 5 



species, or the transfer to other widely separated localities 

 of species already in Britain. Marsh plants, of all the 

 groups, are the least likely to be introduced accidentally 

 or on purpose by man. 



Many of the heath or barren-land plants might be 

 classed equally well as marsh species, for gravelly or 

 sandy areas tend to become peaty and waterlogged in 

 our climate. The most marked characteristic of this flora 

 is the occurrence in it of certain gregarious plants, which 

 occupy definite areas in enormous profusion, though 

 entirely absent from others equally suitable. Several of 

 our heaths, for instance, are very local, though all of them 

 occur abundantly where found at all. The British plants 

 which have a marked western geographical distribution 

 within the Islands nearly all belong to the marsh and 

 heath groups. 



Of the other open-land groups, that belonging to good 

 soil and clayey meadows is surprisingly restricted, and 

 many of the species are probably late introductions. It 

 is not difficult to see the reason why we have so few 

 species characteristic of our wide areas of clayey pasture. 

 These, till recent times, were woodland, not open prairie, 

 and since the destruction of the woods they have been 

 under cultivation or closely grazed. We have therefore 

 nothing equivalent to the prairie vegetation of North 

 America or other drier climates. Several plants confined 

 to the eastern counties belong, however, to this group ; for 

 there the dry cutting winds of winter probably always 

 prevented the forest growth from extending to the sea, 

 even where the soil was richest. The other meadow 

 species have generally a wide range throughout Britain, 

 wherever the climate is suitable. 



Our woodland plants are extremely difficult to deal 

 with, partly on account of the wholesale destruction of the 



