THE CONTINENTAL FLORA OF SOUTH SWEDEN 371 



western Sweden and in southeastern Norway (Cirsium; cf. p. 411). Euphorbia, 

 on the other hand, is lacking in Denmark, and is not found on the west coast 

 of Sweden until the north of Halland and Bohuslan, and moreover it has an 

 area of distribution in the south-east of Norway. In these districts it most often 

 grows on sea-shores. Perhaps we may imagine a direct dispersal to these parts 

 by sea-currents from the southern coasts of the North Sea. Unlike the other, 

 Euphorbia has also an eastern distribution brancii, comprising Oland and Gotland. 

 There it grows in marshes, mostly on peat soil. 



Some species have a peculiar general distribution. From Middle Russia they 

 extend far towards the west across North Germany, but further to the south 

 they reach their western limit much earlier or are entirely lacking; such are 

 Bidens radiatus, Cardamine parviflora, Scolochloa festucacea, and Senecio palustris. 

 Sonchus palustris has a similar distribution. It is abundant in the north-west of 

 Germany, and in Holland and Belgium, and it also has a few occurrences in 

 the south-east of ICngland, while in France it is to be seen only in some few 

 scattered places. We have already had an opportunity of noticing this type of 

 distribution (see p. 364). 



Several species have their occurrences in South Sweden situated on the Cen- 

 tral Swedish lowlands. They may have a few occurrences scattered right across 

 the lowlands, e. g. Bidens radiatus, Cardamine parviflora, and Scirpus radi- 

 cans — or they may be restricted to the eastern parts, such as Scolochloa 

 festucacea (the Motala River and some lakes through which that river flows in 

 Ostergotland). As all these species are found in North Germany (though there, 

 as generally in its distribution, Bidens is highly sporadic), it is remarkable that 

 the species are altogether lacking in the extreme south of Sweden. If we imagine 

 that the immigration of these species into Central Sweden took place direct from 

 the east, we should observe that Bidens and Scirpus have their nearest occur- 

 rences in this direction situated so far away as the extreme east of Finland or 

 in Estland and Lettland, while Cardamine, as well as Scolochloa, on the other 

 hand are, distributed over almost the whole of the extreme south of Finland. 

 For the first-named species, therefore, a long-distance dispersal must have taken 

 place. 



Achroanthes monophyllos is distributed in a similar way in Sweden (see Plate 21). 

 Its distribution-area in Central Scandinavia forms a continuation of its distri- 

 bution-area in Finland and the east of Balticum. Along North Germany this 

 species does not reach further west than Riigen and Usedom. 



Carex vulpina and Viola uliginosa have a distribution in South Sweden which 

 is well worthy of attention. Both these species are distinctly restricted to the 

 south-east of Sweden. The distribution of Carex vulpina bears a great general 

 resemblance to that of Melampyrum nemorosum (Plate 10; see Samuelson 1922 b, 



