1 905-1906.] Scottish Mountain Plants. 243 



steppes, meadows, marshes, lakes, and deserts, its fauna and 

 flora — may all be epitomised upon a mountain. 



Subject to a remark made above, it will be obvious that 

 the vertical range of vegetation upon any particular mountain 

 largely depends on the latitude, a difference of three degrees 

 benig about equal to a thousand feet in elevation." In 

 Europe, as the Arctic region is approached, there is a very 

 rapid falling away of this vertical range. The flora of the 

 lowlands of Northern Europe is repeated with but slight 

 differences upon the hill summits of that country. In Sc^ot- 

 land, the range of plants is not nearly so marked as in 

 equatorial countries, or even in the European Alps or other 

 like mountain-ranges. There the vegetation frequently ex- 

 tends from the Vine and the Olive region, not far above 

 sea-level, to the borders of perpetual snow. Here we com- 

 mence with grassland or woodland of a more or less Northern 

 type, and end where stragglers from subalpine regions, and 

 even from the lowlands, combine with characteristic plants of 

 the higher parts of mountains to form a dwarf vegetation. 



As islands, Great Britain and Ireland are exposed to in- 

 fluences which do not affect the mountains of large continents. 

 The influence of the sea, with its varied currents, must 

 account in part for the wide difference of levels to which 

 plants ascend in the two islands. 



Comparative Purity of Mountain Floras. 



The changes that take place when virgin ground is devoted 

 to agricultural purposes effect a very considerable influence 

 on the flora. For instance, some of the indigenous plants 

 are quite likely to perish, owing to the breaking up of land 

 by the plough, by irrigation, or draining. If certain plants 

 disappear, however, it is likely enough that others of exotic 

 origin will make an appearance, for amongst the seeds of 

 plants cultivated are sure to be those of foreign weeds, which 

 speedily grow. In some cases the aliens usurp the places of 

 native plants. Such changes as these here indicated have no 

 doubt taken place extensively, especially in such countries as 

 Switzerland, where many of the valleys and lower slopes 

 to-day are highly cultivated vineyards. 



