THP: continental flora of south SWEDEN 311 



While steppe species are thus able to utilize only to a very small extent the 

 localities on ihe sea-shores that have abundance of light, continental species, be- 

 longing to other groups have had greater possibilities of doing so. In treating 

 the distribution of these species we shall have an opportunity of showing the 

 enormous importance the skdrgardar have and have had for the distribution of 

 plant species in South Sweden (Chapter x). 



Of the few steppe species found on the sunn\' cliffs and hillsides on the shores, 

 Silene viscosa should first be called to mind. Its peculiar distribution in the 

 South-Eastern Swedish archipelagoes (p. 325), shows what an unexpectedly great 

 amplitude in relation to external factors the steppe species may have, and how 

 easy it may sometimes be to imagine the distribution of a species in a high 

 degree determined by its capacity of dispersal and the absence of competition 

 with other species. 



Artemisia campestris has a fairly wide distribution on sandy sea-shores. Its 

 northernmost spontaneous occurrences in Sweden, in north eastern Uppland, are 

 situated on shores. 



Hence the occurrence-possibilities of steppe species that we may expect in a 

 South Swedish vegetation untouched by the hand of man, are rather inconsider- 

 able. We should expect to find steppe species in the larger lime districts, 

 especially 071 the rocky pavements of Oland and Gotland, and in the rainless di- 

 stricts on one or other in some way especially favoured, hardly shaded Iiillside, as 

 the OSes especially in eastern Smdland. The quite dilTerent distribution of many 

 steppe species in South Sweden is in the first place to be ascribed to the influ- 

 ence of human activity. 



The Distribution of the species and Arable Land in South Sweden. 



The remodelling activity of civilization on the natural vegetation appears most 

 in the cutting down or thinning of the forests and in the transformation of the 

 woodland into plough-fields or pasture land. 



Among the changes in the flora that take place in consequence of such an 

 influence of civiHzation it should above all be noticed that forest species disappear 

 or become scarcer, new species immigrate, such as weed-species, and certain spe- 

 cies that had in a natural vegetation only minor sporadic localities at their dis- 

 posal may get increased possibilities of distribution owing to the fact that human 

 intervention creates new localities for them and facilitates their spread. 



In South Sweden there arc sharp contrasts between two different types of 

 natural scenery. Extensive forest and mountain districts contrast with large. 



