14 Origin of the British Flora. 



species are more properly desert plants, and are only- 

 confined to the coast because in Britain we have no other 

 suitable regions. -^ 



The aquatic flora consists largely of species of wide 

 range, which have a remarkable power of reaching isolated 

 rivers, lakes, or ponds. Though some of these species are 

 confined to limited areas, most of them tend to re-appear 

 wherever the local conditions are favourable. They are 

 apparently more limited in their northerly range by un- 

 favourable climate than by diflliculty of crossing barriers. 

 Several of the aquatic plants of limited range are almost 

 confined to the East Anglian broads and rivers ; but this 

 limitation is evidently due to the more extensive and 

 connected waterways of that district, rather than to other 

 conditions. Not one of our aquatic plants is a member 

 of the Alpine flora, or belongs to the Lusitanian group 

 found in Cornwall and in the West of Ireland. 



Among the marsh and peat-moss plants are many of 

 which the local distribution is evidently governed by 

 climate and geographical position, and is not dependent 

 on soil or amount of rainfall. A large group of these 

 plants consists of upland forms, such as the Arctic willows 

 and sedges. Another set is confined to the Eastern Counties; 

 though these are few in number, notwithstanding the large 

 area of swampy ground there found. A third group is 

 confined to the South-west of England, or to the West of 

 Ireland. 



The anomalies in the distribution of our peat-moss 

 and marsh plants are very striking, especially as this flora 

 probably has been less aflected by human agency than 

 any other, except the Alpine. Man may have drained 

 a certain number of swamps, and thus exterminated some 

 species, principally in the Fenland ; but it is not probable 

 that he has had much to do with the introduction of new 



