MIDDLE EUROPE. 263 



Empelrum, Vacdnium, and Calluna, with Goodyera repens, Chimaphila umbel- 

 Ma, and Linnaea barealis less frequent. The valleys between the dune ridges 

 show all stages between open water, grass morass, moss morass, swamp 

 meadow, meadow, and pasture on the one hand, and deciduous forest, mixed 

 forest, meadow forest, and swamp forest on the other. 



Sitmsky (1885) has found that most of the high moors of Bohemia have 

 arisen from meadow moors, while all others have come from wet heath: 



The layers of meadow moor have developed in ponds, from the edges of 

 which they have spread as high moors into other places. The change to high 

 moor takes place chiefly at the edges of decaying trees, since Sphagnum develops 

 readily only in contact with an organic stratum, and where there is abundant 

 nm-off after rains. The remains of animals, as well as of plants, Picea 

 excelsa, Acer, Sorbiis, etc., are thought to indicate the great age of the moor 

 stratum. 



Fliche (1886) has described a forest near Nancy in which the beech consti- 

 tutes the central mass, while the periphery consists chiefly of oak : 



The identification of charcoal remains in a city wall showed them to be all 

 of beech and none of oak, indicating that the entire forest consisted once of 

 beech. The author assimied that the outer portions of the forest were cleared 

 for purposes of charcoal-making in the twelfth century, and that the oak took 

 possession, as it was able to thrive in the strong insolation which handicapped 

 the beech. The same author has made a number of studies which have to do 

 with successional changes in forests (1878, 1883, 1886, 1888, 1889). 



Senft (1888) traced the development of vegetation on naked xerophjiiic 

 slopes of the Horselbergen: 



The pioneers were lichens, especially Parmelia, followed soon by mosses, 

 Hypnum, BarbuJa, and after a few years by Festuca ovina, which appeared first 

 in the rock clefts and then spread into a thick sod. The next invaders were 

 all grasses, Koekria cristata, Briza, Melica, and Brachypodium, which almost 

 entirely replaced Festuca in three years; the grasses were then invaded, though 

 not completely replaced, by herbs, Helianlhemum, Verbascum, Lactuca scariola, 

 Agrimonia eupatoria. Anemone, Gentiana, etc., and by a few shrubs, Juniperus 

 communis, Viburnum lantana, and Crataegus. Later appeared lAgustrum, 

 Comus, and Ehamnus, and still later, Cotoneaster, Crataegus, Prunus, and 

 Rosa, forming a thicket 12 years after the inception of the succession. The 

 last stage was a forest of Sorbus, Corylus, Fagus, Alnus, Tilia, and Acer. 



Klinge (1890) has considered in detail the effect of prevailing winds upon 

 the shallowing of water forms: 



Pools, lakes, rivers, and seas are filled not only by the deposit of detritus and 

 organic materials on their bottoms, but also by the activity of plants. The 

 initial point of the process is fovmd in places where the water is not too deep, 

 and where waves and currents do not seriously disturb vegetation. Above 

 all things, such places must be protected from wind, waves, and currents. 

 In lakes and bays, the shore which is most protected from wind during the 

 growing-season is the first one to be colonized, while in rivers it is the bank 

 which is most protected from the action of currents and wind. Ponds and 

 small lakes usually do not show this difference on account of the absence of 

 waves. The initial area and the direction of the filling process conform to the 



