THE CONTINENTAL FLORA OF SOUTH SWEDEN 237 



so numerous compared to those in Western Europe. The comparatively small 

 number of Euboreal species is also remarkable. The reason is that the oak zone 

 in the government of Kazan has a very scanty extent, squeezed in as it is between 

 the coniferous forest district in the north and the steppe region in the south. 



For the present, however, it would not seem possible to carry through the 

 division of the flora of continental Europe amongst the main groups mentioned 

 above. Our knowledge of the northerly limit of the species in the north of 

 Russia is far too defective in many cases to render such a course possible. 

 Consequently it seems to me not to be expedient at preseut to attempt to dis- 

 tinguish between a Meridio-Boreal and a Ubiquitous group, or between a Boreal 

 and a Subarctically Boreal group. In what follows, therefore, I sliall make use 

 of only the following main groups: 



I. Meridional species: in Eastern Europe mainly distributed in the steppe 

 regions. 



II. Mericiio-Borcal species: in Eastern Europe abundantly distributed both 

 in the steppe regions and in the forest region of central (and northern) Russia. 



III. Boreal species: in Eastern Europe distributed mainly in the forest region 

 of central (and northern) Russia. 



IV. Sibirian species. 



As appears from the following pages, however, I have endeavoured to take 

 into consideration the far from uniform range of the species towards the north 

 in Russia in the laying down of distribution-types. 



According to the character of the distribution outside Eastern Europe the 

 species of each of the first three groups may be divided between different lypes 

 of distribution. 



For the distinction and naming of the distribution-types I have discriminated 

 a number of phytogeographical districts in Europe and tried to name the distri- 

 bution-types as briefly as possible after the district or districts comprised in the 

 distribution. I have discriminated the different flora districts in agreement with 

 Engler's system (Engler und Gilg, 1912). In certain districts of minor interest 

 from the present point of view I have simplified the system, and in a few cases 

 I have used areas otherwise delimited. 



The flora districts from which I have thus delimited and named the types of 

 distribution are the following: 



Pontis: The South Russian steppe district and the plains of Hungary and of 

 the northern part of the Balkan Peninsula. 



Dacia: about the lower regions of the East-Carpathians and the North Balkan 

 highlands. 



Danubia: the plains of Hungary and the northern part of the Balkan Penin 

 sula, especially Rumania. 



'7 Ceografiska AnnaUr 1022. 



