672 



a lapse of a long period, mav get to bcar a strong resemblance 

 to that of a neighbo uring country, especially to the flora of Scot- 

 lantl, may be easily understood without adopting the theory of a 

 land connection. Considering that the migration has been going 

 on for ages, it might be assumed that perhaps the entire flora of 

 Scotland has gradually tried to immigrate, and when the natura] 

 conditions (soil and climate) agree so closely with the country 

 whence the immigration has taken place, then the species in their 

 continual struggle for place would ultimately occur in similar quan- 

 tities and associations in the different localities as the species which 

 are met with in corresponding localities in the mother-country. 



Ostenfeld (p. 115 above) is of opinion that if the immigration 

 had taken place across the sea, the flora would have »consisted of 

 fewer species.« But the richness of a flora is dependent on other 

 factors besides the facility with which the immigration takes place 

 and the age of the flora, viz. on how many different sorts of habi- 

 tats the country contains. The richer the country is in differ- 

 ences as regards the habitats, the richer the flora, and as the 

 Færoes presumably in this point also resemble Scotland, and espe- 

 cially the Scottish islands, the flora would hardly be poorer even 

 if it immigrated across the sea. 



Ostenfeld also remarks that in the case of an immigration 

 across the sea the piants introduced would have »developed or 

 been in the aet of developing peculiar forms,« but he gives no 

 reason for this, nor do I see any, the circumstances being as in 

 the present case: the flora being so young as in the Færoes, and 

 the soil and climate agreeing so closely with those of the mother- 

 country. It must naturally also be dependent on the power of 

 variability of the different species; and as the genus Hieracium is 

 highly variable, it is lo be understood that this particular genus 

 has been developing new forms (see Dahlstedt, p. 625 above). 



Several circumstances seem to indicale that an occasional 

 immigration to the Færoes has been taking place across the sea, 

 little by little, during successive ages, and probably down to the 

 present day. Thus, many species, which are met with in a very 

 few, or occasionally in a single locality only, could undoubtedly 

 grow in various other localities than those in which they have 

 been found. 



