326 



R I K A I< D STERNER 



occurrences outside Scandinavia are in 

 north-eastern Germany, where the species 

 belongs to the »Pontische Hugel-forma- 

 tion» and reaches its western Umit so far 

 east as the Oder. Tlic j)rcsent area of 

 distribution in South Sweden can hardly 

 be explained with reference to the in- 

 fluence of geographical factors. The 

 numerous occurrences in l^ohuslan, the 

 countr)' round (Gothenburg and northern 

 Halland show that the habitat amplitude 

 must be ratlier 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 (Jstra harad in 

 Smaland J have several times noted the 

 species spread at roadsides. The present 

 shape of the distribution will probabl\' 

 have to be viewed as not permanent. 

 The species is now undergoing a process of spreading from some older occur- 

 rences, which may possibly be relics and which can in the first instance 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 liuman 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>Briisan» (between the upper Ema-valley and the Ostergotland- 

 houndary) is not fully investigated. Certainly the species occurs on the os slo])es all the way between 

 Ilultsfrcd and Eksjo. 



Fig. iS. Tiie distribution of Potentilla rupestris 



in the Scandinavian North. 



O: localities in whicli the species is a colonist 



or fugitive from cultivation. 



