376 RIKARD STERNER 



The species of the first group, which thus do not reach their distribution- 

 limits within the borders of South Sweden, generally show the unevenness 

 in their distribution by occurring more abundantly in the eastern than in the 

 western part. The primary cause of this is to be found in the nature of the 

 soil. Probably, too, the climate is of some importance, both directly and in- 

 directly. 



The species can be accounted continental cnvint; to their distribution in Central 

 and Western Europe. They are abundantly represented in Central Europe and 

 reach their westerly limits in the western parts of that region. [Ledum forms 

 an exception.] The reasons for these limits are not easy to find; probably the 

 climate is an important factor. We may content ourselves with the knowledge 

 that the factors that come into play here have not brought about any westerly 

 limits in South Sweden. 



The species of the second group scarcely show any uniform features in their 

 distribution. Only this can be maintained, namely that their infrequent occur- 

 rences are situated in the coast regions or the flat regions of Central Sweden. 

 The distribution of these species displays no connection with the continental 

 formation of the land. 



As has already been pointed out, several of these species show in their general 

 distribution the peculiarity that, outside East Europe, they are to be found only 

 or chiefly in the Baltic lowlands. Several of the species are peculiar owing to 

 the rareness of their occurrences throughout their distribution outside East Europe. 

 It even seems as if such a sporadic appearance also characterizes the East Euro- 

 pean distribution of, for instance, Arabis Gerardi, Bidens radiatus, Cardamine 

 parviflora, Scirpus radicans, and Viola uliginosa; but of course these species may 

 have been largely overlooked there. 



The species we have treated in this chapter, are, in the main shade-plants or 

 marsh-plants: they may be said, to some extent, to be the opposite ecologically of 

 the light-loving or dryness-loving steppe species. Consequently we cannot except 

 that their distribution should show a continental character to the same degree 

 as the steppe species. In accordance with this fact also they form a compara- 

 tively insignificant part of the total stock of species in the corresponding type 

 of vegetation. Thus we have now found that the distribution of the species in 

 South Sweden only sliglitly reflects the formation of the region in a continental- 

 maritime respect. There are only one or two species which within the region 

 show distribution limits that can be connected with geographical conditions of a 

 continental type. 



