296 RIKARD STERNER 



present distribution of species, viz. through the fact that the wider dispersal the 

 species have attained thanks to human action has originated in natural occurrences. 



An examination of the possibilities of occurrence of the steppe species in a 

 South Swedish vegetation unaffected by human interference naturally meets with 

 great difficulties. 



Inter alia we must take into consideration that the species may have a fairly great 

 amplitude in relation to their habitats, and appear in a vegetation that is not their 

 normal place of abode. The above grouping of what are here treated as steppe 

 species was based on the normal mode of occurrence. If we now especially attend 

 to the importance for the present distribution of species, that the former occurrence 

 of fully natural, suitable localities may have had, it is of great consequence to notice 

 the capacity of several species to hold on to a locality in what is for them a normally 

 strange vegetation, even if they lead a pining life. Through their organization the 

 species may .survive vegetatively. In South Sweden the steppe species if they ever 

 had similar occurrences there — have generally been highly favoured by human 

 activity and procured considerably increased possibilities of distribution. Yet there 

 are examples of cases of the said kind. Some observations may be given : 



Among the peculiar plant occurrences that characterize the upper Ema valley 

 in north-eastern Smaland there are a few occurrences of the Arctic-Alpine Oxy- 

 tropis campestris. They generally are located on slopes towards the river which 

 are southerly exposed and are made up of fine gravel (see table 2, Appendix II). 

 At Klovdala, in the parish of Jareda, I found (7. VIII. 1918) an individual of 

 the species in a dense pine forest, where it grew in a completely closed ground 

 vegetation of Arctostaphylos uva ursi, Calluna vulgaris, Dicranum majus, and 

 Hylocomium parietinum. It was not flow*ering, but had a pod from the pre- 

 ceding year. 



The great Hogsby ridge, which runs through eastern Smaland from the country 

 round Granna down to the Straits of Kalmar at Pataholm, is, in the western 

 part of the parish of Fagelfors, spread out into a large, partly hilly gravel plain. 

 On southerly exposed slopes in the vicinity there is a very rich herbaceous flora. 

 The level gravel-plain is occupied by a closed pine forest with a ground vege- 

 tation of chiefly mealberry and cowberry. A close examination of an experi- 

 mental area of i m^ showed that in this cover there were inter alia a few sterile 

 individuals of Potentilla arenaria and Viola rupestris and one flowering, but 

 dwarfed individual of Ranunculus polyanthemos (16. VII. 1920). 



It seems to me that importance must be attached to the capacity of certain 

 steppe species to retain by vegetative propagation an occurrence that does not 

 completely correspond to the ecological demands of the species. It might be 

 conceived that they vegetatively hold on to a locality during a longish time, 

 until, for some reason, the habitat changes its nature and becomes better able 



