XU PEEFACE. 



reliance to be placed upon such discoveries, where the personal evi- 

 dence is not convincing, we must be guided by collateral circum- 

 stances depending mainly on the geographical range of the species. 

 There is probably not a single species of flowering plants peculiar 

 to our islands.* Those which are confined to our western counties 

 and to Ireland may generally be traced down the western depart- 

 ments of France to Spain and Portugal ; the mountain plants of 

 Scotland are mostly to be foimd in greater abundance in Norway 

 and Sweden, and often, though at great elevations, in the Alps and 

 Pyrenees ; in oiir eastern counties there are occasionally found a 

 very few of the east European species, which, although extending 

 over the Scandinavian peninsula and Denmark, do not, in central 

 Europe, spread much to the westward of the Rhine ; our southern 

 coasts here and there shelter the extreme northern representatives 

 of species common in the warmer regions of southern Europe ; 

 whilst the bulk of our Flora, the more common inhabitants of our 

 lower hills, plains, and seacoasts, are, in similar situations, more or 

 less spread over the continent of Europe and that vast portion of 

 temperate or northern Asia now under the Russian dominion, ex- 

 tending frequently beyond eastern Siberia to the shores of the 

 Pacific. Plants generally spread over these regions, if only once or 

 twice found, upon tolerable authority, in corresponding stations in 

 this country, may therefore well be admitted as likely to be foimd 

 again ; but, to convince us that a species only known to flourish in 

 the burning districts of the south Mediterranean region grows also 

 on Salisbury Plain, that others should skip from the hot, dry hills of 

 Italy and Greece to the cold, damp mountains of northern England 

 without being found in any intermediate station, or that a subalpine 

 plant of central and southern Europe, which does not there ascend 

 to the high primitive ranges, should have strayed in an isolated 

 locality in the high granite-mountains of northern Scotland, would 

 require stronger evidence than the casual mention by a botanist of 

 the seventeeth century, or the testimony of a gardener, founded on 

 specimens raised from seeds gathered in a summer excursion. 



It is chiefly with a view to illustrating the probable indigenous 

 or adventitious character of the species, that the general geographi- 

 cal area each one occupies is prefixed to its British stations, stated 

 however only in general terms, without investigating very precisely 

 its remote limits, especially towards the south and the east, these 



• The Irish Spiranth (p. 507) is at present the sole exception. 



