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 difficulty 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 
andsedges. Anothersetis 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 affected 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 
