272 RIKARD STERNER 



chiefly only for South-Eastern Sweden; compare Andersson, for instance, 1906 

 and 1910). 



In the vegetation xerothermous species occupied a more prominent position 

 than at present. It is of especially great importance that the nature of the soil 

 must have been quite different to what it is now. In such a dry and hot climate 

 the soil must have been of a continental character even in many localities of 

 another character than those in which, nowadays too, special edaphic conditions 

 may give rise to a more or less continental type of soil. The continental species 

 which are strongly tied to more or less continental soil-types should then have 

 had considerably increased possibilities to extend their areas at the same time as 

 the greater warmth of the summers must have directly influenced their thriving. 



It is thus estabhshed that isolated occurrences of xerothermous continental spe- 

 cies in South Sweden may be explained by the fact that there formerly have 

 existed other climatic conditions more favourable to those species. 



Further, in chapter ix, I will a little more in detail treat the relation between 

 some isolated plant occurrences and the history of the South Scandinavian flora. 



Chapter VI. 



Survey of the continental element in the South Swedish flora. 



From table i (p. 230) it is evident that the South Swedish flora is closely 

 connected with the flora of the central part of the Middle European plain. Of 

 the species of the South Swedish flora 90 % are found in Brandenburg and West 

 Prussia; 85, 84 and 83 %' are in common with Silesia, northern France and Li- 

 vonia. For Kazan, Moscow and South-East England the percentage of species 

 in common is, on the other hand, 62, 66 and 73/0. Taken on an average 

 80 % of the species of the South Swedish flora are in common with that of one 

 of the other special districts, a very high figure, inferior only to the one shown 

 by the Livonian flora, which is 82 %'. 



If, on the other hand, we examine how large a part the species, in common 

 with South Sweden, form of the flora in each of the other special districts, we 

 arrive at the highest percentage, 91, for Livonia, then at 81 and 80 for West 

 Prussia and Brandenburg respectively, the lowest percentages being those of South- 

 East England and Northern France with 71 each and Moscow with 72. The 

 average is here 77 %. If we compare this with the average for the other special 

 districts, we shall find the South Swedish flora occupies an intermediate position; 

 four special districts have a higher average, viz. Brandenburg 86, West Prussia 

 85, Silesia 84, and Northern France 79; five have a lower average, viz. Westphalia 

 76, Livonia and Sout-East England 72 each, Moscow 69, and Kazan 61. 



