I CHAP. Liii BUSH AND FOREST ON ACID HUMUS SOIL 217 



as high-forest (uncinato-pinetum) and in the shade of its trees, which 

 are 10-20 metres in height, there grows a dense underwood composed of 

 shrubs and perennial herbs belonging to high-moor. 



Similar scrub is found on all other high mountains above the limit 



of proper forest. For example, it is met with on high mountains in Japan 



I at altitudes between 2,200 and 2,500 metres, and is here formed by 



Pinus parviflora (which is related to P. Cembra) as well as by birch, Alnus 



viridis, and others. 



In like manner scrub appears in America and in Antarctic lands, and 

 m the latter case is produced by species of Nothofagus. Moreover, in 

 northern Europe the shrubs mentioned on page 197 as occurring on high- 

 moors become so numerous that they form 'large and continuous 

 thickets'^, and there also occurs scrub that is formed of dicotylous trees, 

 such as oak and beech ; the soil is raw humus and the trees are more or 

 less elfin-trees. None of these species, however, occur exclusively in this 

 shape ; they will be discussed in the chapters dealing with mesophytic 

 vegetation. 



* Yapp, 1908. 



