iv.] OF THE ANCIENTS. 137 



of leaves of other trees, and partly from its stifling 

 other plants by its own foliage, and thus obtain- 

 ing exclusive possession of the soil. 



Of the extinction of trees within periods which, 

 although very remote, must in a geological sense be 

 regarded as modern, we have a striking instance in 

 the fact stated by Danish naturalists, and recorded 

 in LyelPs " Antiquity of Man," p. 9, that although 

 the Scotch fir is not a native of the Danish Islands, 

 and when introduced there does not appear to 

 thrive, yet that its trunks are met with in the bogs 

 at various depths, associated with flint implements. 



In the same bogs, but at a higher level, are found 

 prostrate trunks of the sessile variety of the com- 

 mon Oak, and still higher up some of the peduncu- 

 lated variety of the same tree, together with the 

 Alder, Birch, and Hazel. Now the Oak in later 

 times has been almost superseded throughout Den- 

 mark by the Beech. 



Other trees, such as the White Birch, characterise 

 the lower part of the bogs, but disappear from the 

 higher; while others, again, such as the Aspen, 

 Populm tremula, occur at all levels. 



This, and other corresponding facts that might 

 be cited from the animal kingdom, shew, that even 

 under the present conditions of the earth's surface 

 particular plants disappear, and others take their 

 place. 



I have alluded to this fact in a paper read before 

 the Natural History Section of the British Associa- 



