BOTANY 563 



pp. 221-444, 1922), in which he treats of the continental element 

 in the Flora of South Sweden. The author divides the European 

 continental species into four classes, viz. : I. Meridional : 

 species which occur mainly in the steppe regions of East 

 Europe. II. Meridio-Boreal : species found commonly in the 

 Steppe and forest regions of central and northern Russia. 

 III. Boreal : species mainly found in the forest region of 

 central and northern Russia. IV. Siberian species. In each 

 of these classes the distribution type outside eastern Europe 

 is subdivided under a number of headings. Thus Ranunculus 

 illyricits is a Meridional species with a pontic distribution ; 

 Veronica spicata is a Meridio-Boreal species with a pontic 

 and sarmatian distribution whilst Potentilla fruticosa is a 

 Siberian type. Most of the continental (E. European) species 

 show a type of distribution which is central European in 

 character with a western limit which tends to form a boundary- 

 line from north-east Russia in a south-westerly direction to 

 the south-east of France, sometimes with a marked extension 

 into Scandinavia. Towards the south-westerly limit marked 

 discontinuity of distribution is a feature of some species, notably 

 Adonis vernalis. As a class the continental species are regarded 

 as characteristic of soils rich in electrolytes, with a high porosity 

 and power of heat absorption. They, and above all the 

 steppe species, often occur, outside definitely continental 

 climatic conditions, as calcicoles ; a fact which is attributed 

 to a high tolerance for lime and conditions of low humidity 

 unfavourable to other species. Continental species are also 

 mostly heliophiles. The continental species in the south 

 Swedish Flora number about 115, or approximately 12 per 

 cent, of the really native species (casuals, aliens, species of 

 cultivated ground being omitted). The corresponding percen- 

 tage of continental species in the native flora of other areas 

 is 1-2 per cent, for south-east England, 4-9 for northern France, 

 18 per cent, for western Prussia, 26-6 per cent, for Moscow, 

 5 per cent, in Norway, and 8 per cent, in Denmark. In south 

 Sweden the continental element is met with chiefly in the 

 dry meadows, the grass heaths, and on the gravelly ridges of 

 the south Swedish highland. During the Boreal and Sub- 

 boreal periods of early post-glacial times it is suggested that 

 the steppe species probably had a much wider distribution, 

 but under the more oceanic climate of the existing period 

 they are almost restricted to the calcareous or sandy soils, 

 arable land, or the slopes of the gravelly ridges where the 

 dry conditions and high insolation which favour their occur- 

 rence obtain. The study of the continental element suggests 

 that the south-eastern part of Sweden belongs to the floral 

 region of Sarmatia (= East Baltic wood region of Drude), 



