THE CONTINENTAL FLORA OF SOUTH SWEDEN 335 



continental species belonginq; to other vegetation types have a similar distribu- 

 tion, Geranium bohemicum (Plate 12), Ledum palustre, Achroanthes monophyllos 

 (Plate 21), Scutellaria hastifolia (Plate 10). To these might be added many non- 

 continental species, especially certain calciphilous species, as e. g. Carex orni- 

 thopoda, Corydalis pumila and Draba muralis (Plate 8). 



The species might be supposed to have immigrated by an easterly route to 

 south-eastern Sweden and, tor some reason or other, not to have attained its 

 full distribution towards the west (cf. Chapter xi). 



That several clifif-plants spread in south-eastern Sweden are absent in south- 

 western Scandinavia is natural, as suitable localities arc there almost wholly 

 lacking for similar species (for instance, Mclica ciliata (Plate 10) and Sedum 

 album (p. 357). 



Perhaps, in some cases, the cause of these peculiarities in the South Scandi- 

 navian distribution are to be ascribed to the South Swedish highland, making, of 

 course, a hindrance to the interchange of species between central and southern- 

 most Sweden. 



To what extent does the distribution on the other side of the Baltic correspond 

 to the division of the species between the distribution-branches mentioned? We 

 find the remarkable circumstance that several species of the westerly route are 

 missing in a considerable part of north-western Germany. Some species have their 

 westernmost occurrences in the coast districts of northern Germany as far to 

 the east as the country round Stettin: Asperula tinctoria (Plate 15), Crepis prae- 

 morsa, which has, however, an occurrence on Riigen too (Plate 17), Potentilla 

 arenaria (Plate 6), Prunella grandiflora, Pulsatilla pratensis (in Hayek's sense), and 

 Senecio integrifolius (Plate 6). The continental Pulmonaria angustifolia, belonging 

 to another vegetation type, shows the same peculiarities in its distribution. In 

 order to make out the immigration of these species into Western Scandinavia 

 it is, however, not necessary to conceive a former distribution farther in the west 

 in North Germany. A direct immigration across the sea from the neighbour- 

 hood of Stettin into Western Scandinavia may be as possible as a similar one 

 from North-Eastern Germany into South-Eastern Sweden. 



How are the steppe species that are confined to the eastern distribution- 

 branch, spread on the other side of the Baltic? With a couple of exceptions, these 

 species are confined to the eastern part of the North German plain. Polygala 

 comosa and Carex ligerica form the exceptions: they reach their western limits 

 in the east of Hanover. (Of the other continental species, just mentioned, which 

 are lacking in western Scandinavia Scutellaria hastifolia has a remarkably wide 

 distribution in North Germany. It reaches its western limit not until the lower 

 Weser; cf. Chapter xi). 



Here it should be remembered that some steppe species with a wide distri- 



