The Problems of Plant Distribution 263 



on this isolated mountain top is better explained on 

 the theory of migration due to the Glacial epoch. 



The Alpine plants of the temperate regions may 

 be specifically the same as species growing at sea- 

 level in higher latitudes. On the higher summits 

 of the New England mountains and the southern 

 Alleghanies, one sees tufts of the pretty little Green- 

 land sandwort (Arenaria grcenlandica) , which is un- 

 known in the neighboring lowlands, but flourishes at 

 sea-level in Labrador and Greenland; and in the 

 higher regions of the Rocky Mountains as far west 

 as Utah, a beautiful little flower, Dry as octopetala, 

 one of the most characteristic of arctic flowers, is 

 a common and conspicuous species. This species is 

 also abundant upon the mountain summits of 

 Europe. 



ISLAND FLORAS 



Remote islands afford some interesting problems 

 in the evolution of new species. The more remote 

 the island, the less likely that new forms will be 

 brought to its shores, and the more probable that 

 the forms which do so will have time to change, in 

 accordance with the new conditions to which they 

 are subjected. Perhaps the most striking case 

 known is that of the Hawaiian Islands. These are 

 volcanic masses, thrown up from great depths, and 

 separated by long distances from any other land. 

 The islands are of different ages, and evolutionary 



