Periodical Literature. 177 



northern Russia and northern Germany as far south as Vienna, 

 besides the Alps, a wavy line from Calais to the middle Ural 

 forming the southern limit. During this period probably all for- 

 est growth vanished except possibly in the lowest plains of South 

 Germany, northern end of the upper Rhine valley, the lowest 

 Elbe valley in Bohemia, lowlands of Moravia and lower Austria. 



In Western Europe the glaciation reached to the Arctic Ocean ; 

 at the southern limit it seems that plains were adjacent to the ice 

 sheet, and on the southern boundary of the plains region there 

 was found forest country. The lower elevations of the Carpath- 

 ians and the Transylvanian Alps remained forested, as well as 

 the eastern base of the Alps and the Bohemian mountains. The 

 forest country proper of Europe during the ice age was the Med- 

 iterranean portion south of the Alps. This portion since then 

 has been gradually deforested, while the glaciated area to the 

 North had reforested itself. The migrations of plants and es- 

 pecially tree species, which have been studied by palaeobotanists, 

 came in part of old tertiary floral elements from West and South, 

 in part of Eastern elements from Central Asia. Denmark was 

 occupied by the former, Scandinavia both from the South and 

 from the East by way of Finland, whence spruce and White 

 Alder came, while middle Europe was entirely reforested from 

 the south. The studies of peat bogs have revealed layers with 

 typical tree remnants ; at the bottom the tundra flora is found, 

 Dryas octopetala and various Salices as characteristic plants, then 

 follows birch, aspen and soon pine, then oak and alder and 

 lastly beech. Supposedly this is the sequence of re-occupation. 



It is interesting to note, that while pine in prehistoric times 

 formed extensive stands in Denmark, since historic times it is 

 here entirely absent. During this domination of the pine, broad- 

 leaved shrubs and trees came in, such as Sorbus, Wild Cherry, 

 Snowball, Alders, then denoting warmer climate, Hazel, Elm and 

 Linden. Gradually the pine was replaced by Oak accompanied 

 by Ash, Maple, Elm, denoting further improvement of climate, 

 and across the then existing land bridge, it progressed as far as 

 middle Sweden, where it met in competition with the spruce. 

 The beech, with its tolerance a dangerous competitor of the oak, 

 came in at the end of prehistoric and the beginning of historic 

 times crowding out the oak, until it met the spruce at a lower 

 latitude — being a later comer than the oak. Later the climate 



