THE CONTINENTAL FLORA OF SOUTH SWEDEN 313 



woodless or poorly wooded arable lands. The South Swedish highland that 

 forms a broad zone almost across South Sweden separates the Skane — South- 

 Halland arable plain from the large Central Swedish plains which are in their 

 turn separated from one another by minor wooded mountain districts: Kolmarden 

 between Ostergotland and the vale of Malar, Tiveden between the latter and the 

 plain of Vastergotland (see fig. 8). 



These main features in the character of the landscape clearly reappear in the 

 distribution of plant species in South Sweden. Many southerly xerophilous and 

 heliophilous species are limited to the plains, whereas northerly or Central 

 European "montan'-subalpine elements have their occurrences in the forest 

 districts. 



A species, whose occurrence is in the highest degree characteristic of the 

 arable fields of South Sweden is Avena pratensis. 



It is an important feature of the type of scenery of the South Swedish arable 

 plains that the cultivated fields are here and there broken by uncultivated spots 

 marked by mounds of moraine or of Archaean rock, rising like islets out of the 

 »clay sea», or by oses running bandlike across the plain (cf. Sernander »i90i a», 

 p. io8). 



In these uncultivated spots, as on balks, waysides etc., the vegetation is formed 

 of more or less xerophilous herbaceous hillsides (Swed. ^^drtbackar^-)), in which 

 Avena pratensis is such an important constituent that its distribution in South 

 Sweden nearly corresponds to that of the large arable areas (cf. the vegetation 

 analyses in Tables i and 2, Appendix II. See the map on Fig. 9; this map is incom- 

 plete concerning southern Skane, the coast district of Halland, western Vastergot- 

 land, and, probably, some parts of southern Varmland, especially the peninsula 

 Ndset). It is interesting that such details in the distribution of the arable land 

 districts as the occurrences in certain river valleys and near certain lakes in 

 Smaland, are corresponded to by Avena occurrences. The distribution in Norway 

 shows the same good agreement with the distribution of arable districts. Arable 

 fields of some importance are found in the country round the Christiania-Fjord 

 and the valleys just to the north of it, in south-westernmost Norway on Jaderen 

 and in the neighbourhood of Trondhjem, where Avena also occurs. 



The character of the South Scandinavian distribution of Avena pratensis also 

 appears clearly if the distribution-map of that species is compared with the map 

 showing the distribution of Pulsatilla veriialis, which is tied to the heath-like 

 forest communities in sterile sandy or gravelly soil. (See figures g and 10). 



Hence, in the distyibtiiion of Avena pratensis we have a picture of the maxi- 

 mum distribution of the rich herbaceous hillside flora of South Sweden. 



On these herbaceous hillsides a great number of the steppe species of the 

 South Swedish flora have their most numerous abodes. We find a remarkably 



