264 SUCCESSION IN EURASIA. 



direction of the prevailing winds. When this is west, succession develops 

 swamps, moors and meadows on the protected west shores, while the east 

 shores are still actively eroded by the waves. Klinge has also traced the 

 action of vegetation, e. g., Butomus, Sagittaria, Glyceria, Acorus, Phragmites,. 

 Sdrpus, etc., in producing plant bars in rivers, and causing them to become 

 more or less completely overgrown. 



Sitensky (1891) has given an exhaustive account of the moors of Bohemia: 



He points out that the basic division into low and high moors was known 

 to Eiselen in 1802, and that while Sendtner sought to explain this division 

 on soil properties, Lorenz referred it to the amount of water. Meadow moors 

 (lowland, valley, or inland moors of Eiselen, grass moors of Lorenz, chalk- 

 moors of Sendtner, and infra-aquatic moors of Lesquereux) are termed Arundi- 

 neta when dominated by Phragmites, Typha, and Glyceria, Cariceta with Carex, 

 and Cariceto-arundineta when mixed. When colonized by Salix and Alnus, 

 they form alder swamp. Through drainage, meadow moors become meadows. 

 High moors (heath moors. Sphagnum moors, supra-aquatic moors) are initiated 

 in Bohemia mostly by Sphagnum rigidum; Viola palustris is regarded as an 

 early indicator of moor development. They show finally a number of different 

 shrubs and trees, Pinus, Abies, Betula, Caliuna, Rubu^, Andromeda, etc. 



Klinge (1892) has assumed that Picea excelsa is now in intensive migration 

 from the east to the west of Europe, and has endeavored to establish its suc- 

 cessional relations to the other dominants of north Europe. His results are 

 essentially like those of Sernander for Scandinavia: 



The seedling of the spruce demands moisture and shade, and its ecesis is 

 difficult or impossible on dry sandy or rocky soil covered with Cladonia rangi- 

 ferina and CaUuna vulgaris, in which Pinups silvestris constitutes the climax 

 community. When, in consequence of fire and other accessory causes, such 

 pine forests produce a layer of "ortstein," the conditions for swamping the 

 area obtain. Often after fire in pine forests, pine and birch appear together, 

 but the birch disappears in a generation, and the pine dominates the final 

 community. If, however, a cover of Hylocomium and Hypnum are present, 

 the growth of pine is hindered and the birch is favored. The birch forest 

 affords just the moistxire and shade needed by the spruce, and the latter 

 quickly replaces the birch. The spruce likewise replaces the oak with its 

 greater light requirement, as is true also of Populus tremvla and Tilia. The 

 willow forests of river and lake shores are regarded as final commimities, except 

 where drying permits the entrance of Alnv^, which in turn is replaced by Picea. 



Krauze (1892) has advanced the following conclusions as to heath in Ger- 

 many (cf. Focke, 1871, 1872, and Borggreve, 1872): 



(1) Heath is originally a part of the communal area used for pasture, fire- 

 wood, etc. 



(2) The Caliuna heath, which extends from Scotland to Mecklenburg and 

 Liineburg, is not to be regarded as a wilderness, but as a half-culture formation. 



(3) The occurrence of open heath in the northwest and its absence elsewhere 

 is conditioned solely by utilization. 



(4) Many, though not all, existing Caliuna heaths were once forested. 

 Caliuna is regarded as belonging to the pine association. 



Krause (1892) regards the meadows of Germany as half-culture formations, 

 owing their existence to the influence of man, as he assumes to be true of 

 heath also: 



