234 RI K A RD STERNER 



Table 2. The mode of occurrence of continental species in some special 

 districts on the Middle European plain. 



Table 2 shows the summary. From this it follows: 



1. that the continental element has representatives in all the types of vegetation 

 set up; 



2. that — naturally — the great majority of species belong to the steppe or 

 steppe-like vegetation. The few continental species of the western districts 

 belong to a great extent to this type; 



3. that out of the comparatively small number of species belonging to other types 

 of vegetation, some (particularly those of the types 6 and 8) are found in a 

 considerable part of the continent of Middle Europe, while others (especially 

 those of the types 4, 9 and 10) seem to have a conspicuously easterly distri- 

 bution. 



The great number of continental species of the type 7 may be remarkable. 

 The type of forests in question has another character in more maritime parts 

 of Middle Europe than in Central and East Europe. Certain trees that are im- 

 portant in the Central and East European mixed oak forests, are missing in 

 western Europe, and in the ground vegetation this type of forests has several 

 continental species which are so physiognomically conspicuous as to give it a 

 special character (e. g. Anemone hepatica and ranunculoides, Corydalis-species, 

 Gagea-species, Pulmonaria-species, and Viola mirabilis). On the other hand, several 

 of the species characterizing the ground vegetation in the West European type 

 have a more maritime distribution (e. g. Euphorbia amygdaloides, Carex laevigata, 

 Lysimachia nemorum, Potentilla sterilis, Scilla non-scripta, Teucrium scorodonia, 

 Veronica montana, Vinca minor). Moreover it should be pointed out that, from 

 a biological point of view, some of the continental species occupy a separate po- 

 sition. They are early spring plants and are consequently adapted to a short ve- 

 getative season. The peculiar biology of these species has been treated by 

 Hesselman 1904 (see, e. g., p. 451) and Sernander 1906 (pp. 381 ff.) among others. 



