^yS Norivay and the Noj'wegians 



Norway, we must suppose that there were repeated 

 changes of climate, several thousands of years of a 

 severer climate, during which the northern and eastern 

 species immigrated, followed by thousands of years 

 during which the milder climate favoured the immi^ra- 

 tion of the flora from the south and south-west, com- 

 pelling the older flora, less suited to this change of 

 temperature, to retreat. In this manner the climate 

 must have changed several times since the Glacial Age, 

 and the distribution of plants must have changed in 

 accordance. 



Professor Blytt gives, as proof of alternating dry and 

 rainy periods in the climate of the Scandinavian 

 Peninsula, the result of his investigations in Norwegian 

 bogs — besides referring to those of Professor Steenstrup 

 in the Danish bogs — in the oldest of which he has, by 

 boring, found four layers of peat, separated by three 

 layers of stumps of trees, some standing upright, showing 

 four wet periods during which the four layers of peat 

 were formed, separated by three drier periods, when the 

 growth of the peat was arrested, and the bogs covered 

 with trees. 



When a dry period was succeeded by a moist period, 

 the continental species, that is, the species which shun 

 the coast, became rarer, and when a moist was followed 

 by a dry period, the plants which love moisture became 

 scarce. 



The mode of immigration is still a matter of surmise, 

 but it is probable that the migration of the greater part 

 of the present flora, during the gradual change of 

 climate, has proceeded slowly and step by step across 

 connected tracts of country. 



