178 



EILIF DAHL 



Lastly. I have considered limnic species growing in fresh water as adapted to 

 long-distance dispersal since there is some evidence that such plants are 

 easily spread by water birds. 



If the Amphi-Atlantic plants attained their present area by long-distance 

 dispersal one would expect plants with adaptations to long-distance dispersal to 

 be more numerous within the Amphi-Atlantic elements as compared to other 

 elements which presumably immigrated across more or less continuous 

 land connections. Table 1 gives a breakdown of the Scandinavian Arctic- 

 Alpine flora according to adaptations to distance long-dispersal and phyto- 

 geographic elements. A two-way grouping is obtained, a so-called contingency 



Table 1 



Comparison of the Arctic-Alpine Elements in the Flora of Fenno-Scandia as to 

 Phytogeographic Elements and Adaptations to Long-distance Dispersal 



Taraxacum and Hieraciiim excluded from the enumerations. 

 [Upper figure == observed, lower figure (in brackets) = statistically expected number of 



species per element.] 



Other western 

 Amphi-Atlantic 

 species 



20 



(17.7) 



4 

 (5.7) 





 (0.5) 





 (0.2) 



(0.9) 



25 

 10.0% 



table, and by standard methods it can be tested whether there is any correla- 

 tion or contingency between the subdivision in phytogeographic elements and 

 dispersal groups. The figures expected under assumption of no correlation or 

 contingency are given in brackets. 



In general the numbers observed agree quite well with those expected, 

 assuming that no contingency and no statistically significant discrepancies 

 occur. There is a slight under-representation of types adapted to long-distance 

 dispersal in the western Amphi-Atlantic element and this observation can be 

 used as an argument against the hypothesis that they immigrated by long- 

 distance dispersal. 



