326 



RIKARD STERNER 



Fig. 1 8. The distribution of Potentilla rupestris 



in the Scandinavian North. 



O: localities in which the species is a colonist 



or fugitive from cultivation. 



occurrences outside Scandinavia are in 

 north-eastern Germany, where the species 

 belongs to the »Pontische Hugel-forma- 

 tion» and reaches its western limit so far 

 east as the Oder. The present area of 

 distribution in South Sweden can hardly 

 be explained with reference to the in- 

 fluence of geographical factors. The 

 numerous occurrences in Bohuslan, the 

 country round Gothenburg and northern 

 Halland show that the habitat amplitude 

 must be rather great and cannot be sup- 

 posed to form a hindrance to a continued 

 distribution. Evidence in favour of this 

 view is to be found in the fact that the 

 species has been observed as a colonist 

 or as a plant fugitive from cultivation in 

 other parts of the country, for instance 

 in tv.o localities in Narike and one in 

 Uppland (Vaksala). In Ostra harad in 

 Smaland I have several times noted the 

 species spread at roadsides. The present 

 shape of the distribution will probably 

 have to be viewed as not permanent, 

 a process of spreading from some older occur- 

 relics and which can in the tirst instance be 



The species is now undergoing 



rences, which may possibly be 



ranged with Falbygden and Ostra harad [cf the distribution of Dracocephalum 



Ruyschiana (Plate 4), Pulmonaria angustifolia (Plate 4), and Lathyrus hetero- 



phyllus (Plate 4)]; and this process is greatly assisted by human activity directly 



as a vehicle and indirectly by creation of suitable localities. 



The peculiar distribution of Potentilla arenaria (Plate 3 and 6) in eastern Sma- 

 land and Blekinge would seem to some extent to be explained in a similar 

 manner. The species is much spread on the oses, but just outside the present 

 boundary there, probably are localities of value equal to those inside.^ Thanks 

 to human intervention (the species is to a great extent spread along the road- 

 sides, the seeds probably accompanying the road gravel), the species is being 

 spread from the few natural localities it may have had in the district; and the 



* The OS in the valley of the rivulet y>Brusan» (between the upper Ema-valley and the Ostergotland- 

 boundary) is not fully investigated. Certainly the species occurs on the os slopes all the way between 

 Hultsfred and Eksjo. 



