512 



0. Stapf. 



what then is that southern element which undoubtly is present in the 

 British flora and has so early attracted the attention of British botanists 

 by its peculiar distribution, mostly westward, frequently much interrupted 

 and in many cases extremely limited? If we take a British flora, for 

 instance, the last edition (1904) of Babington's »ManuaU and a flora of 

 Germany, like Koch's » Flora Germanica*, ed. Ill, whose area after the 

 deduction of the Mediterranean districts in Switzerland and Austria and the 

 extreme West is practically that of Central Europe, and if we mark off in 

 the British flora those species which are not recorded from Central Europe 

 as defined, we obtain a rough list of the plants which do not*partake in 

 the composition of the flora of Central Europe. Of these a small number 

 is peculiar to Northern Europe, or, outside Great Britain and Ireland, only 

 known from North America; these may be struck off. If we further revise 

 with the help of the latest floras the distribution of the species remaining 

 on the list partly to exclude errors, and partly to add such British species 

 as in isolated cases enter' the Central European region either from their 

 headquarters in the west or south, we shall have left an assemblage of 

 about 150—160 species, (9*^/o of the British flora) the European continental 

 areas of which lie mainly along the west coast of Europe from Holland 

 and Belgium or from Normandy to Spain and Portugal, or beyond those 

 countries to Italy and even the Orient. They fall into two fairly distinct 

 classes. That set which does not extend into the eastern Mediterranean 

 region may be called for the purposes of the paper the Atlantic element, 

 the other the Mediterranean. The Atlantic element extends in Belgium and 

 France more or less eastward, but crosses the Rhine or the Rhone only 

 in exceptional cases. A few species referred to it reach North Italy, but 

 outside the typically Mediterranean region. A few also extend along the 

 west coast to Denmark or Norway, but they have in each case their main 

 area farther south. I have grouped those species in 3 classes: 



i. Species generally found in and near cultivated land, 



2. Species confined to the coasts (littoral species). 



3. Species other than those referred to classes 1 and 2. 



All the species 1) enumerated are considered as native in Great Britam 

 and Ireland with the exception of some of class 1 and one or two of 

 classes 2 and 3 which may be denizens rather than natives. Exception may 

 be taken to the inclusion or exclusion of certain species; but I think their 

 number is so small that the broad conclusions for which the lists may 

 serve as a basis, will not be affected thereby. Moreover, no classification 

 of this kind can be absolute, unless it is made artificial or arbitrary. 



i] The species ot Rosa, Jiubits and Uieracium have not been taken into consider- 

 ation owing to the difficulty of a satisfactory collation of the species recognised by 

 British and continental authors. 



